KAFKA-3219: Fix long topic name validation

[vahidhashemian]

This fixes an issue with long topic names by considering, during topic
validation, the '-' and the partition id that is appended to the log
folder created for each topic partition.

[vahidhashemian]

@granthenke Thanks for the suggestion. I did not want to assume anything on the first try, but if it is acceptable to assume a max value for partition count I'd be happy to update the pull request.

[granthenke]

@vahidhashemian I would be interested in thoughts from others.

[gwenshap]

I think 249 characters and 99,999 partitions is a good solution.
We need to document this as a limitation, but it sounds acceptable to me.

[vahidhashemian]

Sounds good to me. With 249 characters for topic name we can actually have 100,000 partitions (since partition ids start from 0). I'll try to find the right place in the documentation to mention this limitation.

[gwenshap]

Oh, I think you removed the behavior where long names cause an error when creating the topic. I actually preferred that to silent truncating of the name. Any reason you removed this part?

[vahidhashemian]

@gwenshap Well, the only change to the actual code now is the topic name length limit which is decreased from 255 to 249. Topic names longer than the limit would cause an error like before, and would not be truncated. Could you please clarify? I might be missing something.

[granthenke]

@gwenshap Any reason this can't get into 0.10?

[gwenshap]

@granthenke Well, lack of LGTM at the moment.
I'll try to get to it this week, but can't promise.

[granthenke]

@gwenshap gotcha. This patch reduces the valid topic name length to 249 (from 255) and adds test coverage and documentation. It's a LGTM for me.

@vahidhashemian Anything else you need to do yet for this patch?

[gwenshap]

LGTM