Incorrect casing of schemaName parameter on the API results in IllegalArgumentException on case-insensitive database setups

[raju-saravanan]

In some scenarios, Schema Registry throws an IllegalArgumentException when the database is using case-insensitive queries and the casing of schemaname API parameter are different from actual schema names.

Steps to reproduce:

1. Configure case-insensitive database collation in Schema Registry database.
2. Create a schema called "test".
3. Invoke the API: /schemas/TEST/versions?branch=MASTER
   The above API request will result in a similar exception:

com.google.common.util.concurrent.UncheckedExecutionException: java.lang.IllegalArgumentException: value already present: 1