docs: align EDB endpoint table and config params with controller code

[kichasov]

Summary

Three small corrections in docs/howto/DBaaS Operator.md found during a code-vs-docs audit. No behavior changes.

#	Fix	Why
1	EDB success row: 200 OK / 201 Created (was: only 201 Created)	aggregator_client.go:151 accepts both: resp.StatusCode() != http.StatusOK && resp.StatusCode() != http.StatusCreated
2	Add 410 / 422 to the EDB aggregator-rejection table	client/types.go:191–199 IsSpecRejection covers 400, 403, 409, 410, 422 — all five route to InvalidConfiguration / AggregatorRejected. DD endpoint table already listed all five; EDB was inconsistent.
3	Add DBAAS_AGGREGATOR_URL env var to the Service Parameters table	cmd/main.go:107 reads it with default http://dbaas-aggregator:8080; Helm chart does not set it. Documenting the override path for cross-cluster setups.

Test plan

• Doc rendering verified (3 lines changed, no structural changes)
• Each claim cross-checked against the cited code line