fix-7984: Show test/live key of Stripe under Payments section

[ghost]

Fixes #7984

Short description of what this resolves:

Show test/live key of Stripe under Payments section

Changes proposed in this pull request:

• Create new record "stripe_mode" on table Setting
• Response new column "stripe_mode" when user Get or Update Setting

Checklist

• I have read the Contribution & Best practices Guide and my PR follows them.
• My branch is up-to-date with the Upstream development branch.
• The unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

• All the functions created/modified in this PR contain relevant docstrings.

[norbusan]

@lthanhhieu

thanks for the PR, a few comments:

Fixes #7984

This is not the correct issue, please link the correct issue.

Also, please fix the Codacy Static Code Analysis, look into the details, it is simple, there is one unused import.

Thanks