feat: Implement m2m table for container_registries, and groups

[jopemachine]

Implement AssociationContainerRegistriesGroups as m2m table of container_registries, and groups for resolving #1908.

Note

#1908 mentions both user and project, but since project needs to be implemented first, this PR stack addresses only the project aspect.
Refer to #1960 for adding an association table with the User table and related tasks.

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue

[jopemachine]

• feat: Implement Image Rescanning using Harbor Webhook API #3116
• feat: Implement CRUD API for managing Harbor per-project Quota #3090
• feat: Implement ImageNode, ImageNodes as per-project images API #3036
• feat: Implement Image RBAC project scope #3035
• feat: Implement APIs for associating, disassociating container_registries with groups #3067
• feat: Implement m2m table for container_registries, and groups #3065 👈 (View in Graphite)
• main

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[jopemachine]

Previously, there was no per-project image lookup functionality, so data migration logic will be unnecessary here.

[fregataa]

How about adding the new table definition in an existing file such as models/container_registries.py or models/groups.py? This is just a suggestion, you don't need to reflect it right away.

[jopemachine]

How about adding the new table definition in an existing file such as models/container_registries.py or models/groups.py? This is just a suggestion, you don't need to reflect it right away.

Personally, I think it’s better to place them in separate files.
Having a single file for each table, rather than defining multiple tables in one file, seems more intuitive and makes it easier to refer back to them later.