Do a final commit on end consumer group generation for immediate comm…

…its (segmentio#715)

* Do a final commit on end consumer group generation for immediate commits

* add test for final commit on generation end

Co-authored-by: rhansen2 <rob.hansen@sendgrid.com>

Revert "Nettest fix (segmentio#788)" (segmentio#824)

This reverts commit 2e02f37.

SASL Mechanism: AWS MSK IAM (making requested edits) (segmentio#798)

Co-authored-by: Achille <achille.roussel@gmail.com>
Co-authored-by: Christian Maher <maher.cs@gmail.com>

Nettest fix (segmentio#788)

* don't skip messages when offset == highwatermark

Allow Writer to automatically create topics. (segmentio#775)

* set AutoCreateTopic when requesting metadata in Writer

if a metadata request is made with auto create topic set,
we now make a metadata request to trigger the topic creation
if the topic is not already in the cache and update the cache
after the request is made.

Makes Assignments nullable in createpartitions RequestTopic (segmenti…

…o#758)

Add Transactionalmessage interface for request routing (segmentio#744)

* Add TransactionalMessage interface.

Add TransactionMessage interface so the Transport
automatically routes messages to Transaction Coordinators
if required.

Add Code of Conduct and Contribution Guidelines (segmentio#699)

* Add Code of Conduct and Contribution Guidelines

Add a full Code of Conduct and Code Contribution Guidelines document.
Provide description on how best to retrieve code, fork, checkout, and commit changes.

Fixes segmentio#688

* Update steps for git push

* Update based on PR comments

Removed several linkable sections in the Code of Conduct.
Update contributing to use kafka-go consistently.
Finished explaining how to replace the original version with forked version of the library.

* Update based on further feedback

* Adjust to follow the twilio-go code of contact

Preserve message order across batches. (segmentio#716)

* Preserve message order across batches.

Co-authored-by: Michael Graf <mikegraf000@gmail.com>