Get subject config result to 404

[loicgreffier]

When performing a kafkactl get schemas or kafkactl get schema <schema>, the compatibility mode recovery almost always results to HTTP 404 due to no compatibility applied to subject which leads to trouble with internal management.

Solution:

• Use ?defaultToGlobal=true query param to avoid getting HTTP 404

Impact:

• With the solution above, we lose the information about: for a subject, does the compatibility come from the global compatibility applied to the schema registry or from the subject itself (GLOBAL). Seems acceptable

[loicgreffier]

?defaultToGlobal=true will be handled internally, no need to add it to Ns4Kafka