fix: incorrect SR authorization message is displayed

[spena]

Description

Fixes a few error messages caused by SchemaRegistry authorization errors.
For instance, this error was displayed when attempting to create an AVRO stream without SR schem access:

ksql> create stream avro with (kafka_topic='avro', value_format='avro');
Schema registry fetch for topic avro request failed.
Caused by: Unrecognized token 'User': was expecting ('true', 'false' or 'null')

	at [Source: (sun.net.www.protocol.http.HttpURLConnection$HttpInputStream); line:
	1, column: 6]; error code: 50005

The new fixed error just adds a new line at the end of an old SR access error. In a secured SR environment, SR returns an authorization error even if the Subject does not exist.

ksql> create stream avro with (kafka_topic='avro', value_format='avro');
Avro schema for message values on topic avro does not exist or you do not have permissions in the Schema Registry.Subject: avro-value
Possible causes include:
- The topic itself does not exist	-> Use SHOW TOPICS; to check
- Messages on the topic are not Avro serialized	-> Use PRINT 'avro' FROM BEGINNING; to verify
- Messages on the topic have not been serialized using the Confluent Schema Registry Avro serializer	-> See https://docs.confluent.io/current/schema-registry/docs/serializer-formatter.html
- The schema is registered on a different instance of the Schema Registry	-> Use the REST API to list available subjects	https://docs.confluent.io/current/schema-registry/docs/api.html#get--subjects
- You do not have permissions to access the Schema Registry.Subject: avro-value	-> See https://docs.confluent.io/current/schema-registry/docs/security.html

Same error fix when attempting to insert data:

ksql> insert into avro(id) values(1);
Failed to insert values into stream/table: AVRO
Caused by: Not authorized to write Schema Registry subject: [avro-value]

This is similar to the current authorization error thrown by Kafka:

ksql> insert into avro(id) values(1);
Failed to insert values into stream/table: AVRO
Caused by: Not authorized to access topics: [avro]

Testing done

Manual verification.

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[agavra]

lgtm!

[agavra]

Suggested change

	throw new KsqlException("Could not serialize row: " + row, e);
	break;