Add Support for Multi-Platform Image Manifests

This commit add support for retrieving image manifest if the images
provides multiple platform variants, e.g. amd64, arm64, …. It also
provide better HTTP responses if the API client provided an image that
doesn't exist, if the authentication for the image doesn't work or if
anything else failed for the image manifest retrieval.

Fixes #125

Develop.md

@@ -2,7 +2,7 @@ This file provides some hints and examples how to develop PREvant.
 
 # Backend Development
 
-You can build PREvant's backend API with [`cargo`](https://doc.rust-lang.org/cargo/) in the sub directory `/api`. For example, `cargo run` build and starts the backend so that it will be available at `http://localhost:8000`. 
+You can build PREvant's backend API with [`cargo`](https://doc.rust-lang.org/cargo/) in the sub directory `/api`. For example, `cargo run` build and starts the backend so that it will be available at `http://localhost:8000`.
 
 When you than interact with the REST API to deploy service, it is worthwhile to have a look into the [Traefik dashboard](https://doc.traefik.io/traefik/operations/dashboard/#the-dashboard) to double check if PREvant exposes the services as expected.
 
@@ -29,8 +29,6 @@ For developing against a local Kubernetes cluster you can use [k3d](https://k3d.
 3. Deploy some containers and observe the result [here](http://localhost/master/whoami/):
 
    ```bash
-   # PREvant can't handle multi arch images, yet (see https://github.com/aixigo/PREvant/issues/125)
-   # Therefore, the example uses 1.8.1 which hasn't multi arch versions
    curl -X POST -d '[{"serviceName": "whoami", "image": "quay.io/truecharts/whoami:1.8.1"}]' \
       -H "Content-type: application/json" \
       http://localhost:8000/api/apps/master