Add JIRA webhook secret handling and update tests for webhook calls

[ToxicBiohazard]

Types of changes

What types of changes does your code introduce?
Put an x in the boxes that apply.

• Bugfix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).
• Documentation Update (if none of the other choices applies).

Proposed changes

Updated the codebase to use Jira Webhook v2. As Jira Webhook v1 will be deprecated.

Checklist

Put an x in the boxes that apply.

• I have read and followed the CONTRIBUTING.md
  doc.
• Lint and unit tests pass locally with my changes.
• I have added the necessary documentation (if appropriate).

[ToxicBiohazard]

Unsure, why it failed. I've forgotten to add the variable name in the .test.env file

[dimoschi]

The webhook_call function is now too specific, while it should remain as generic as possible.

[dimoschi]

LGTM

[ToxicBiohazard]

This PR is not needed. I learned later that the password can be appended to the end of the URL as per webhook v2.0. Apologies, for the inconvenience this may have caused.

[dimoschi]

No worries @ToxicBiohazard this is something new! Thanks for taking care of it in the first place!