Database: project reference model

[lachmanfrantisek]

Follow-up for: packit/research#128

The current situation with project/trigger/commit-related models:

• Project for trigger not effective to get for multiple entries.
• JobTriggerModel is more a git reference than a trigger.
• Commit is spread across the models (in build/test models and release).

Let's transform JobTriggerModel into something better-named and better-connected. We would like to use it as a project/git reference.

• @lachmanfrantisek promise to explain this task and showcase it via the diagram
• Pick a better name for JobTriggerModel (something like ProjectReference or CommitModel).
• Add a new column for commit hash (e.g. commit/commit_hash/ commit_sha).
• Connect the model directly to the ProjectModel. Each commit occurrence (e.g. pr x branch push) will have a different model -- so, no change in the behaviour...;)
  • With this, we can simplify a lot of queries that try to get a project model throught the pr/branch/release/issue model. Either fix it (if you think it's simple) or create a follow-up card to do it.
• Create migration steps that add the newly introduced connections/values also for the already present data.
• Regenerate the database diagram

[majamassarini]

I re-open it, since just one step has been done.

[majamassarini]

Step 2) blocked waiting for feedback on #2070
Step 3) I prefer not to duplicate data, I re-searched the possibility of using views here