feat: add DESCRIBE functionality for connectors

[agavra]

Description

Implements functionality to describe a connector.

Testing done

Unit testing and local test:

ksql> DESCRIBE CONNECTOR "jdbc-connector2";

Name                 : jdbc-connector2
Type                 : io.confluent.connect.jdbc.JdbcSourceConnector
State                : RUNNING
WorkerId             : 10.200.7.69:8083

 Task ID | State   | Error Trace
---------------------------------
 0       | RUNNING |
---------------------------------

 Source Name           | Kafka Topic | Type
---------------------------------------------
 JDBC_CONNECTOR2_USERS | jdbc2-users | TABLE
---------------------------------------------

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 #")

[cpettitt-confluent]

Mostly questions and a few suggestions.

[cpettitt-confluent]

Minor: Isn't this where the action happens? If so, would this be better suited for "when"?

[agavra]

I suppose so! I thought that the "action" happens when stopAsync() is called (e.g. it calls triggerShutdown which in turn causes the wakeup/close, but I think it makes sense to put it in "when' as well. Will make that change.

[cpettitt-confluent]

This is looking pretty close to me. I think some doc or other clarification on the output of describe would be super helpful. What do you think?

[cpettitt-confluent]

Let's use "KSQL Sources" for now. Otherwise LGTM.

[cpettitt-confluent]

LGTM!