Mastodon PostgreSQL SSL Configuration

This document addresses issues related to configuring SSL/TLS for Mastodon when using the Zalando PostgreSQL Operator.

Symptom: Mastodon Rails/Sidekiq/Streaming processes fail TLS handshakes due to an inability to locate the PostgreSQL CA certificate.
Rationale: Mastodon applications specifically look for their TLS bundle at /opt/mastodon/.postgresql/root.crt. Incorrect mount paths (e.g., /etc/ssl/certs/pgbouncer-ca.crt) are ignored by the application.
Fix: Mount the CA certificate at the expected Mastodon location (/opt/mastodon/.postgresql/root.crt). Ensure environment variables DB_SSLMODE=verify-ca and DB_SSLROOTCERT=/opt/mastodon/.postgresql/root.crt are correctly configured.

Key configuration changes:

Environment Variable Update:
- Key line changed: DB_SSLROOTCERT=/opt/mastodon/.postgresql/root.crt
- Symptom: TLS handshake failed.
- Rationale: Mastodon only reads /opt/mastodon/.postgresql/root.crt. This change updates the DB_SSLROOTCERT environment variable to point to Mastodon's expected CA certificate location, preventing "file not found" errors and ensuring proper TLS configuration.
Explicit Environment Variable Injection:
- Key lines changed:
```
env:
  - name: DB_SSLMODE
    value: verify-ca
  - name: DB_SSLROOTCERT
    value: /opt/mastodon/.postgresql/root.crt
```
- Symptom: Inconsistent database connection behavior across Mastodon replicas.
- Rationale: Explicitly injecting both DB_SSLMODE=verify-ca and DB_SSLROOTCERT=/opt/mastodon/.postgresql/root.crt into each Mastodon workload (web, Sidekiq, streaming, migrate) ensures consistent and secure database connections across all scaled replicas.

Align with Application Defaults: Always verify where your application (e.g., Mastodon) expects TLS files to be located, rather than solely relying on where they're mounted. For Mastodon, the default location is /opt/mastodon/.postgresql.

To validate your changes, run the following commands:

kustomize build applications/web/mastodon/
npm run build