chore(alerts): Remove incidentseen and incidentsubscription models

[ceorourke]

Another follow up to #81522 to remove the unused models. A final PR will follow to drop the tables.

[github-actions]

This PR has a migration; here is the generated SQL for src/sentry/migrations/0800_rm_incidentseen_incidentsubscription.py ()

--
-- Alter field incident on incidentseen
--
SET CONSTRAINTS "sentry_incidentseen_incident_id_008cf29b_fk_sentry_incident_id" IMMEDIATE; ALTER TABLE "sentry_incidentseen" DROP CONSTRAINT "sentry_incidentseen_incident_id_008cf29b_fk_sentry_incident_id";
--
-- Alter field user_id on incidentseen
--
ALTER TABLE "sentry_incidentseen" ALTER COLUMN "user_id" DROP NOT NULL;
--
-- Alter field incident on incidentsubscription
--
SET CONSTRAINTS "sentry_incidentsubsc_incident_id_6d439453_fk_sentry_in" IMMEDIATE; ALTER TABLE "sentry_incidentsubscription" DROP CONSTRAINT "sentry_incidentsubsc_incident_id_6d439453_fk_sentry_in";
--
-- Alter field user_id on incidentsubscription
--
ALTER TABLE "sentry_incidentsubscription" ALTER COLUMN "user_id" DROP NOT NULL;
--
-- Moved model IncidentSeen to pending deletion state
--
-- (no-op)
--
-- Moved model IncidentSubscription to pending deletion state
--
-- (no-op)

[ceorourke]

When I generated the 2nd part of removing the models from code it also generated this:

migrations.AlterUniqueTogether(
    name="incidentsubscription",
    unique_together=None,
),
SafeRemoveField(
    model_name="incidentsubscription",
    name="incident",
    deletion_action=DeletionAction.MOVE_TO_PENDING,
),

but it did the same in #81264 and I had removed it without issue.

[markstory]

Since you're going to be dropping the table shortly, the AlterUniqueTogether operation isn't that important as postgres will drop the constraint when the table is dropped.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #81605      +/-   ##
==========================================
+ Coverage   80.45%   80.50%   +0.05%     
==========================================
  Files        7241     7241              
  Lines      321452   322387     +935     
  Branches    20807    20807              
==========================================
+ Hits       258621   259537     +916     
- Misses      62432    62451      +19     
  Partials      399      399              

[github-actions]

🚨 Warning: This pull request contains Frontend and Backend changes!

It's discouraged to make changes to Sentry's Frontend and Backend in a single pull request. The Frontend and Backend are not atomically deployed. If the changes are interdependent of each other, they must be separated into two pull requests and be made forward or backwards compatible, such that the Backend or Frontend can be safely deployed independently.

Have questions? Please ask in the #discuss-dev-infra channel.

[markstory]

Looks good to me, constraints are being removed and columns made nullable alongside the state update for table removal 👍

[markstory]

Since you're going to be dropping the table shortly, the AlterUniqueTogether operation isn't that important as postgres will drop the constraint when the table is dropped.