ci: Update CI.

.github/workflows/api.yml

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+name: Check API
+
+on:
+  push:
+    branches: [ main ]
+    paths:
+      - '**.rs'
+      - '**.toml'
+      - '.github/workflows/**'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '**.rs'
+      - '**.toml'
+      - '.github/workflows/**'
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  semver:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Setup | Install cargo-semver-checks
+        run: cargo install cargo-semver-checks --locked
+
+      - name: Setup | Checkout code
+        uses: actions/checkout@v3
+
+      - name: Check for SemVer violations | pop3-codec
+        run: |
+          cd pop3-codec
+          cargo semver-checks check-release

.github/workflows/build_and_test.yml

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+name: Build & Test
+
+on:
+  push:
+    branches: [ main ]
+    paths:
+      - "**.rs"
+      - "**.toml"
+      - ".github/workflows/**"
+  pull_request:
+    branches: [ main ]
+    paths:
+      - "**.rs"
+      - "**.toml"
+      - ".github/workflows/**"
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-hack
+
+      - name: Check
+        run: cargo hack check --workspace
+
+  test:
+    strategy:
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Setup | Install toolchain
+        run: |
+          rustup toolchain install stable --profile minimal
+          rustup toolchain install nightly --profile minimal
+
+      - name: Setup | Install cargo-fuzz
+        run: |
+          cargo install cargo-fuzz
+
+      - name: Setup | Cache dependencies
+        uses: Swatinem/[email protected]
+        id: cache
+        with:
+          cache-all-crates: true
+
+      - name: Test | Everything w/o fuzzing (macOS, Ubuntu)
+        if: matrix.os != 'windows-latest'
+        run: |
+          for build_mode in "" "--release";
+          do
+            for feature_mode in "" "--all-features";
+            do
+              echo "# Testing" ${build_mode} ${feature_mode}
+              cargo test --workspace ${build_mode} ${feature_mode} --doc
+              cargo test --workspace ${build_mode} ${feature_mode} --all-targets
+            done
+          done
+
+      - name: Test | Everything w/o fuzzing (Windows)
+        if: matrix.os == 'windows-latest'
+        run: |
+          $build_modes = @('','--release')
+          $feature_modes = @('','--all-features')
+
+          foreach ($build_mode in $build_modes) {
+            foreach ($feature_mode in $feature_modes) {
+              echo "# Testing" ${build_mode} ${feature_mode}
+              cargo test --workspace ${build_mode} ${feature_mode} --doc
+              cargo test --workspace ${build_mode} ${feature_mode} --all-targets
+            }
+          }
+
+      - name: Test | Limited fuzzing (Ubuntu)
+        if: matrix.os == 'ubuntu-latest'
+        run: |
+          for fuzz_target in $(cargo +nightly fuzz list);
+          do
+          echo "# Fuzzing ${fuzz_target}";
+          cargo +nightly fuzz run --features=ext ${fuzz_target} -- -dict=fuzz/terminals.dict -max_len=256 -only_ascii=1 -runs=25000
+          done
+
+  minimal-versions:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Setup | Install toolchain
+        run: |
+          # 1.65 is the Minimum Supported Rust Version (MSRV) for pop3-codec.
+          rustup toolchain install 1.65 --profile minimal
+          rustup toolchain install nightly --profile minimal
+
+      - name: Setup | Cache dependencies
+        uses: Swatinem/[email protected]
+        id: cache
+        with:
+          cache-all-crates: true
+
+      - name: Check
+        run: |
+          cargo +nightly update -Z minimal-versions
+          cargo +1.65 check --workspace --all-targets --all-features
+          cargo +1.65 test --workspace --all-targets --all-features
+        env:
+          RUSTFLAGS: -Dwarnings
+
+  audit:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Audit dependencies
+        uses: EmbarkStudios/cargo-deny-action@7257a18a9c2fe3f92b85d41ae473520dff953c97
+
+  clippy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Install toolchain
+        uses: actions-rs/toolchain@88dc2356392166efad76775c878094f4e83ff746
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+          components: clippy
+
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Check for common mistakes and missed improvements
+        uses: actions-rs/clippy-check@b5b5f21f4797c02da247df37026fcd0a5024aa4d
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --all-features
+
+  formatting:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Install nightly toolchain
+        uses: actions-rs/toolchain@88dc2356392166efad76775c878094f4e83ff746
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+          components: rustfmt
+
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Check code formatting
+        run: cargo +nightly fmt --check

.github/workflows/coverage.yml

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+name: Measure test coverage
+
+on:
+  push:
+    branches: [ main ]
+    paths:
+      - '**.rs'
+      - '**.toml'
+      - '.github/workflows/**'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '**.rs'
+      - '**.toml'
+      - '.github/workflows/**'
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Setup
+        run: |
+          rustup component add llvm-tools-preview
+          cargo install grcov
+
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Measure test coverage
+        env:
+          RUSTFLAGS: "-Cinstrument-coverage"
+          LLVM_PROFILE_FILE: "coverage-%m-%p.profraw"
+        run: |
+          cargo test -p pop3-codec --all-features
+          grcov . \
+            --source-dir . \
+            --binary-path target/debug \
+            --branch \
+            --keep-only 'pop3-codec/src/**' \
+            --output-types "lcov" \
+            --llvm > coveralls.lcov
+
+      - name: Upload to Coveralls
+        uses: coverallsapp/github-action@v2
+        with:
+          format: lcov
+          file: coveralls.lcov

.github/workflows/issue_opened.yml

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+name: Process opened issues
+
+on:
+  issues:
+    types:
+      - opened
+
+jobs:
+  add-to-project:
+    name: Add opened issue to project board
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/[email protected]
+        with:
+          project-url: https://github.com/users/duesee/projects/2
+          github-token: ${{ secrets.ADD_TO_PROJECT_PAT }}