docs: klip-62: Ruby client (#8865)

* docs: intent for klip-62: ksqlDB Ruby client

* Remove KLIP from proposal PR

* KLIP 62 Ruby client discussion

* Remove README.md klip reference

* Scopes update

* KLIP Updates

* KLIP Update

design-proposals/klip-62-ksqldb-ruby-client.md

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+# KLIP 62 - ksqlDB Ruby Client
+
+**Author**: Lapo Elisacci (@LapoElisacci) | 
+**Release Target**: TBD | 
+**Status**: _In Discussion_ | 
+**Discussion**: TBD
+
+**tl;dr:** Develop a Ruby HTTP2 Client to request ksqlDB REST API
+
+## Motivation and background
+
+Allow Ruby / Ruby on Rails developers to get started with ksqlDB.
+
+## What is in scope
+
+* A lightweight but complete Ruby client, kslqDB host and port will be configurable.
+* The Client will handle most of the operations the Java one does:
+
+- Receive query results one row at a time
+- Receive query results in a single batch
+- Terminate a push query
+- Insert a new row into a stream
+- Create and manage new streams, tables, and persistent queries
+- List streams, tables, topics, and queries
+- Describe specific streams and tables
+- Get metadata about the ksqlDB cluster
+- Manage, list and describe connectors
+
+* Documentation and examples
+
+## What is not in scope
+
+* Anything that concerns the ksqlDB development itself.
+* Defining an ORM to dynamically build SQL Statements. (It will get handled by a future project)
+
+## Value/Return
+
+To be able to easily include ksqlDB in any Ruby / Ruby on Rails applications.
+
+## Public APIS
+
+* A class will expose a `config` method to configurate the connection between the client and ksqlDB, like so:
+
+```Ruby
+  Ksql.configure do |config|
+    config.host = 'http://localhost:8088'
+  end
+```
+
+### Methods
+
+- **ksql** - Allows statement to be requested against the /ksql endpoint.
+- **close_query** - Allows closing persistent queries by requesting the /close-query endpoint.
+- **stream** - Allows to perform push queries, processing messages one at a time in a streaming fashion.
+- **query** - Allows to perform pull queries.
+- **cluster_status** - Allows to introspect the ksqlDB cluster status.
+- **health_check** - Allows to check the health of the ksqlDB server.
+- **info** - Allows to get information about the status of a ksqlDB Server.
+- **terminate** - Allows to terminate the cluster and clean up the resources, or to delete Kafka Topics.
+
+## Design
+
+* A Ruby class will implement the logic to request all ksqlDB REST API available endpoints.
+* Request responses will get wrapped inside objects to easily manipulate the returned data.
+
+## Test plan
+
+Both unit and integration tests.
+CREATE, DESCRIBE, DROP, INSERT, SELECT (both push and pull), SHOW and TERMINATE statements will get properly tested, to ensure the client always behaves as expected.
+
+The standard Ruby RSpec test suite will do.
+Testing requests will get performed against ksqlDB >= 0.22
+
+## LOEs and Delivery Milestones
+
+The Gem's under development and most of the endpoints are already covered.
+A first release is expected to be live by the end of March 2022.
+
+Any meaningfull future bug will get handled within a week.
+
+## Compatibility Implications
+
+The client will be compatible with Ruby >= 2.6
+
+## Security Implications
+
+The client will support all protocols supported by the ksqlDB REST API.