[CORL-3061] Allow external mod phases to set `moderationAction`'s and interoperate with DSA mode active

[nick-funk]

What does this PR do?

• Allow external mod phases to run when DSA is enabled
• Allow external mod phases to set the moderationAction which will create moderation actions when rejecting/approving comments
• Allow users to set the rejectionReason when supplying a moderationAction

These changes will impact:

• [X] commenters
• [X] moderators
• [X] admins
• [ ] developers

What changes to the GraphQL/Database Schema does this PR introduce?

None

Does this PR introduce any new environment variables or feature flags?

No

If any indexes were added, were they added to INDEXES.md?

None

How do I test this PR?

• Spin up utilities/externalModPhase with an npm i && npm run start in that directory

• Spin up Coral

• Go to the Admin and enable DSA under General > Digital Services Act feature set

• Under Admin > Moderation Phases Add an external mod phase pointing to http://localhost:7000/api/rejectWithReason

• Using a commenter account, post a comment

• See the comment get rejected

• Check the user's notifications and see that a notification is shown with how it was rejected

• Head back to admin and disable the external mod phase

• Make a new mod phase, point it to http://localhost:7000/api/approve

• Post a comment with the commenter again

• See that the comment is approved

Were any tests migrated to React Testing Library?

No

How do we deploy this PR?

No special considerations.

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