Create cross namespace secrets (#1490)

* Create cross namespace secrets

* add test cases

* fixes

* Fixes
- include namespace in secret name only when namespace is provided
- use username.namespace as key to pgUsers only when namespace is
  provided
- avoid conflict in the role creation in db by checking namespace
  alongwith the username

* Update unit tests

* Fix test case

* Fixes

- update regular expression for usernames
- add test to allow check for valid usernames
- create pg roles with namespace (if any) appended in rolename

* add more test cases for valid usernames

* update docs

* fixes as per review comments

* update e2e

* fixes

* Add toggle to allow namespaced secrets

* update docs

* comment update

* Update e2e/tests/test_e2e.py

* few minor fixes

* fix unit tests

* fix e2e

* fix e2e attempt 2

* fix e2e

Co-authored-by: Rafia Sabih <rafia.sabih@zalando.de>
Co-authored-by: Felix Kunde <felix-kunde@gmx.de>

docs/reference/operator_parameters.md

@@ -172,11 +172,11 @@ under the `users` key.
 
 ## Major version upgrades
 
-Parameters configuring automatic major version upgrades. In a 
+Parameters configuring automatic major version upgrades. In a
 CRD-configuration, they are grouped under the `major_version_upgrade` key.
 
 * **major_version_upgrade_mode**
-  Postgres Operator supports [in-place major version upgrade](../administrator.md#in-place-major-version-upgrade) 
+  Postgres Operator supports [in-place major version upgrade](../administrator.md#in-place-major-version-upgrade)
   with three different modes:
   `"off"` = no upgrade by the operator,
   `"manual"` = manifest triggers action,
@@ -275,11 +275,14 @@ configuration they are grouped under the `kubernetes` key.
 
 * **secret_name_template**
   a template for the name of the database user secrets generated by the
-  operator. `{username}` is replaced with name of the secret, `{cluster}` with
-  the name of the cluster, `{tprkind}` with the kind of CRD (formerly known as
-  TPR) and `{tprgroup}` with the group of the CRD. No other placeholders are
-  allowed. The default is
-  `{username}.{cluster}.credentials.{tprkind}.{tprgroup}`.
+  operator. `{namespace}` is replaced with name of the namespace (if cross
+  namespace secrets are enabled via EnableNamespacedSecret flag, otherwise the
+  secret is in cluster's namespace and in that case it is not present in secret
+  name), `{username}` is replaced with name of the secret, `{cluster}` with the
+  name of the cluster, `{tprkind}` with the kind of CRD (formerly known as TPR)
+  and `{tprgroup}` with the group of the CRD. No other placeholders are allowed.
+  The default is
+  `{namespace}.{username}.{cluster}.credentials.{tprkind}.{tprgroup}`.
 
 * **cluster_domain**
   defines the default DNS domain for the kubernetes cluster the operator is