Finalize deploy token sharding key migration and add DB constraint

Sharding keys for deploy_tokens were backfilled in !160526 (merged). When the background migration is complete, we can complete the sharding key:

• Finalize the BackfillDeployTokensShardingKey background migration - !166556 (merged)
• Finalize the DeleteOrphanedDeployTokens background migration - !166557 (merged)
• Fix factory to always create associated project/group - !169868 (merged)
• Add a multi column not null constraint on project_id and group_id - !206820 (merged)
• Update the database dictionary to show the sharding key is now ready for use - !204129 (merged)