Ensure tag name and relationship uniqueness

[nscuro]

Description

Ensures tag name and relationship uniqueness.

• Adds missing (unique) index on tag names.
• Adds composite primary keys to all join tables of tag relationships. Thus prevents duplicate entries, and voids the need for indexes on individual columns.
• Changes tag relationships from ordered Lists to Sets. We don't need ordering here, and it only adds overhead.
• Changes equals and hashCode of Tag to be based on name, rather than id.
• Removes and re-wires any duplicate records during the DB migration.

Addressed Issue

Fixes DependencyTrack/hyades#1755

Additional Details

N/A

Checklist

• I have read and understand the contributing guidelines
• This PR fixes a defect, and I have provided tests to verify that the fix is effective
• This PR implements an enhancement, and I have provided tests to verify that it works as intended
• This PR introduces changes to the database model, and I have updated the migration changelog accordingly
• This PR introduces new or alters existing behavior, and I have updated the documentation accordingly

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.00% (target: -1.00%)	✅ 85.42% (target: 70.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (7dea143)	27762	22009	79.28%
Head commit (b8a135e)	27770 (+8)	22015 (+6)	79.28% (+0.00%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#1124)	48	41	85.42%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[sahibamittal]

LGTM 👍🏼

[nscuro]

@sahibamittal Had to rebase this PR to resolve a merge conflict caused by #1126. Please have another look when you get the chance!

[nscuro]

I did a final test run with duplicate records across all tag tables, and the migration ended up failing with:

cannot ALTER TABLE "NOTIFICATIONRULE_TAGS" because it has pending trigger events

This happened when the migration tried to add primary keys. It turns out that, if a table has deferred foreign key constraints, you cannot modify rows and alter the table schema in the same transaction: https://github.com/friek/til/blob/master/postgres/alter-table-pending-triggers.md

The solution is to disable deferred constraints during the transaction, such that foreign keys are checked immediately and cannot block table altering.