* Add namespace validation in the client
Signed-off-by: F. Gold <fgold@vmware.com>

* Add namespace validation in the backup controller
Signed-off-by: F. Gold <fgold@vmware.com>

* Add changelog for PR 4057
Signed-off-by: F. Gold <fgold@vmware.com>

* Update Copyright notice
Signed-off-by: F. Gold <fgold@vmware.com>

* Update include_excludes_test.go to follow Go standards and be easier to read
Signed-off-by: F. Gold <fgold@vmware.com>

* Add unit tests for namespace validation functions
Signed-off-by: F. Gold <fgold@vmware.com>

* Make changes per review comments

- use one set of namespace validation logic instead of writing two
- remove duplicate namespace validation functions and tests
- add namespace validation tests in includes_excludes_test.go
Signed-off-by: F. Gold <fgold@vmware.com>

* Return all ns validation err msgs as error list
Signed-off-by: F. Gold <fgold@vmware.com>

* Make error message more clear
Signed-off-by: F. Gold <fgold@vmware.com>