## Description
> Should include a concise description of the changes (bug or feature),
it's
> impact, along with a summary of the solution
## PR Checklist
> Thank you for opening a Pull Request! Before submitting your PR, there
are a
> few things you can do to make sure it goes smoothly:
- [ ] Make sure you reviewed
[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [ ] Make sure to open an issue as a
[bug/issue](https://github.com/googleapis/genai-toolbox/issues/new/choose)
before writing your code! That way we can discuss the change, evaluate
designs, and agree on the general idea
- [ ] Ensure the tests and linter pass
- [ ] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)
- [ ] Make sure to add `!` if this involve a breaking change
🛠️ Fixes #<issue_number_goes_here>
---------
[Cassandra](https://cassandra.apache.org/_/cassandra-basics.html) is a
NoSQL distributed database. By design, NoSQL databases are lightweight,
open-source, non-relational, and largely distributed. Counted among
their strengths are horizontal scalability, distributed architectures,
and a flexible approach to schema definition.
Cassandra go driver link -
https://pkg.go.dev/github.com/apache/cassandra-gocql-driver/v2
This PR
- adds a new source for cassandra
- adds a new tool _cassandra-cql_ with support for executing predefined
parameterized CQL queries on cassandra
- adds unit and integration tests for the tool and the source
- adds documentation for the cassandra source and cassandra-cql tool
---------
Co-authored-by: Wenxin Du <117315983+duwenxin99@users.noreply.github.com>
Co-authored-by: duwenxin <duwenxin@google.com>
