Updates Couchbase integration to support collections

[chedim]

References #3395

This PR introduces new CouchbaseCollectionSession class that can be accessed from CouchbaseSession via CouchbaseSession::collection method. It also updates sinks, sources and flow constructors and their signatures to work with collections.

All of these are breaking changes.

Please note that, although fascinated by the framework and some language features, I am not very familiar with either alpakka or scala and more of a Java dev. So, any suggestions on how to improve my changes are greatly appreciated.

Cheers!

[lightbend-cla-validator]

Hi @chedim,

Thank you for your contribution! We really value the time you've taken to put this together.

Before we proceed with reviewing this pull request, please sign the Akka Contributors License Agreement:

https://www.lightbend.com/contribute/cla

[chedim]

Hi @chedim,

Thank you for your contribution! We really value the time you've taken to put this together.

Before we proceed with reviewing this pull request, please sign the Akka Contributors License Agreement:

https://www.lightbend.com/contribute/cla

Working on it. Hopefully, it'll not take long 🤞

[lightbend-cla-validator]

Hi @chedim,

Thank you for your contribution! We really value the time you've taken to put this together.

Before we proceed with reviewing this pull request, please sign the Akka Contributors License Agreement:

https://www.lightbend.com/contribute/cla

[ennru]

We have received the CLA.

[chedim]

We signed the CLA. Authorized logins: chedim and deniswrosa

[sebastian-alfers]

Closing and re-opening to trigger the CLA validator again.

[chedim]

@ennru @sebastian-alfers @leviramsey Could somebody please review the PR whenever they get a chance? Thank you!