Add kafka_get_watermarks() function

[zilder]

This is a PR for the issue #33. Along with adding new function I also did a bit of refactoring mainly related to KafkaFdwGetConnection() in order to make it more versatile.

[rapimo]

looks good to me.
However we kafka_fdw--0.0.1.sql should bot be touched as we introduce a new version here.
Review and adjustments would be easier if you develop on a branch of the same repo, this way I can't add simple commits and need to hand back changes to you

[zilder]

However we kafka_fdw--0.0.1.sql should bot be touched as we introduce a new version here.

I didn't touch kafka_fdw--0.0.1.sql, I just added it to the repo because before it was generated by make in the build time.

Review and adjustments would be easier if you develop on a branch of the same repo, this way I can't add simple commits and need to hand back changes to you

I pushed watermarks_func to the main repo. Should I create a new pull request?

[zilder]

Oh, now I see that kafka_get_watermarks() was added to kafka_fdw--0.0.1.sql by accident..

[zilder]

..fixed this and also merged with master

[rapimo]

mmmh now it's not mergable anymore, can you rebase onto master?

[rapimo]

@zilder can finalize this?

[zilder]

yes, actually i didn’t see any conflicts

[rapimo]

well github says so:

This branch cannot be rebased due to conflicts
Rebasing the commits of this branch on top of the base branch cannot be performed automatically due to conflicts encountered while reapplying the individual commits from the head branch.