feat(seer-infra-telemetry): Add GcpServiceAccount model for tracking per-org service accounts

[shashjar]

PR 3/4 for CW-1691

Adds a new GcpServiceAccount model to track GCP service accounts created in the sentry-connectors project for the GCP MCP org-level integration. Each Sentry org gets at most one SA, stored in this model so it can be reused across setup attempts and prevent orphaned SAs from accumulating as a result of abandoned integration flows.

This PR is the model-creation migration only; the model will be used in the follow-up PR — #120266.

https://app.notion.com/p/sentry/GCP-MCP-Org-Level-Integration-39f8b10e4b5d8030ba01cd62373641df

[github-actions]

This PR has a migration; here is the generated SQL for src/sentry/migrations/1145_add_gcp_service_account.py

for 1145_add_gcp_service_account in sentry

--
-- Create model GcpServiceAccount
--
CREATE TABLE "sentry_gcpserviceaccount" ("id" bigint NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY, "date_updated" timestamp with time zone NOT NULL, "date_added" timestamp with time zone NOT NULL, "organization_id" bigint NOT NULL UNIQUE, "service_account_email" varchar(255) NOT NULL);

[wedamija]

Do we need an index here? Will we ever need to look things up by email?

[shashjar]

hmm i don't think so. i think we would always be going from org -> SA, and any context in which we already have the SA the organization should be known as well

[cursor]

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[github-actions]

This PR has a migration; here is the generated SQL for src/sentry/migrations/1146_add_gcp_service_account.py

for 1146_add_gcp_service_account in sentry

--
-- Create model GcpServiceAccount
--
CREATE TABLE "sentry_gcpserviceaccount" ("id" bigint NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY, "date_updated" timestamp with time zone NOT NULL, "date_added" timestamp with time zone NOT NULL, "organization_id" bigint NOT NULL UNIQUE, "service_account_email" varchar(255) NOT NULL);