[ritojoao]

Hi, and thank you for maintaining the operator.

This is a small fix for #3230.

Problem: execCreateDatabaseSchema() ignored errors from execAlterSchemaDefaultPrivileges(), and syncPreparedSchemas() skipped schemas that already exist. If granting failed once (for example because a reader/writer role was missing), the sync reported no error and the privileges were never retried.

Change:

• Return the errors of the default privilege statements from execCreateDatabaseSchema().
• Run the schema statements for existing prepared schemas, too. CREATE SCHEMA IF NOT EXISTS and ALTER DEFAULT PRIVILEGES are idempotent, so missing privileges get fixed on the next sync.
• Add a unit test with a fake database/sql driver covering the failure, the retry and the recovery.

One trade-off: default privileges are re-applied on every sync. I am happy to change the approach if you prefer another one.

Testing (golang:1.26.4 container):

• gofmt -l on the changed files: clean
• go generate ./... and go vet ./pkg/cluster/: OK
• go test ./pkg/cluster/ -run TestPreparedSchemaPrivilegeErrors -v: PASS
• go test ./pkg/cluster/: OK
• with database.go and sync.go reverted to the base commit, TestPreparedSchemaPrivilegeErrors fails

I did not run the e2e suite.

Fixes #3230