Feature: Add option for single triggered job

[solarlodge]

Testing done

### Submitter checklist
- [x] Make sure you are opening from a **topic/feature/bugfix branch** (right side) and not your main branch!
- [x] Ensure that the pull request title represents the desired changelog entry
- [x] Please describe what you did

[cdelmonte-zg]

@solarlodge thank you for the PR. can you tell me something more about this feature? Tnx

[solarlodge]

@solarlodge thank you for the PR. can you tell me something more about this feature? Tnx

@cdelmonte-zg Sure :) The original idea derived from the gitlab plugin's webhook somehow -- having an endpoint that belongs to one job exclusively. For several reasons the approach of having a single endpoint for all pipelines + some fancy matching-magic after recieving the webhook didn't fulfill our needs. We came to recognize that we can circumvent the issues we had with our setup by using a single jenkins job that acts as a proxy pipeline. Our setup is now:

• Any PR action of any repository triggers the proxy pipeline
• This pipeline gets all the neccessary informations from the payload
• Based on some values of the payload the according "real" pull-request pipeline is triggered by the proxy pipeline

To realize this we had to at plugin's site:

• Introduce a global configure option at $JENKINS_URL/configure that is of type form and:
  • if empty -> triggers normal behavior
  • if non-empty and job exists -> bypass the iteration over all items of type job and triggers the global configured pipeline
  • if non-empty and job does not exist -> does nothing at all and logs a WARNING at global jenkins log

[cdelmonte-zg]

@solarlodge All right, this is an interesting idea. Perhaps you would like to describe it in the readme and in the docs (a copy and paste from the readme is fine) https://github.com/jenkinsci/bitbucket-push-and-pull-request-plugin/blob/master/docs/index.md ? This would give more context to other users interested in this feature... Thanks a lot

[solarlodge]

@cdelmonte-zg You're absolutely right m( Added this to the docs.

[cdelmonte-zg]

Hi @solarlodge, is your jenkins version >= 2.361.4? I'm asking because I'm updating the plugin to work with Java 17 and I'd like to release the features you've introduced with version 3.0.0 later this week.

Otherwise, if your Jenkins version is < 2.361.4, I'll schedule an extra release, say the 2.9.0, before I release the 3.0.0.

[solarlodge]

@cdelmonte-zg It's Jenkins 2.414.2 (LTS). According to the jenkins java support policy it shouldn't be an issue :)