fix: account for revoked licenses and staff users in auto-apply logic

[adamstankiewicz]

Description:

Extends auto-apply subscription license business logic and tests to include:

• Check for revoked subscription licenses (i.e., no auto-apply with revoked license).
• Check for being explicitly linked to the requested enterprise customer (i.e., no auto-apply as an unlinked staff user).

These additional checks ensure parity with existing business logic around auto-applied subscription licenses in the frontend (source).

Jira:
ENT-9813

Merge checklist:

• ./manage.py makemigrations has been run
  • Note: This must be run if you modified any models.
    • It may or may not make a migration depending on exactly what you modified, but it should still be run.

Post merge:

• Ensure that your changes went out to the stage instance
• Deploy to prod instance

[iloveagent57]

Couple small suggestions, looks good otherwise!