Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1883816

Description of problem:
When creating a new authsource with an existing authsource name, appropriate error message to be shown.

Version-Release number of selected component (if applicable):
Satellite 6.8.0 Snap 16.0

How reproducible:
Always

Steps to Reproduce:
1.Administer -> Authentication Sources -> `Create LDAP Authentication Source`
2.Create authsource with default values(Example: Name=Test_authsource)
3.Create another authsource with same `Name` as above.

Actual results:
No error message is shown.

Expected results:
We cannot have same name for two authsource.