Schema registry

[jrevillard]

Dear all,

Here is an MR for #50.

This work is based on the POC that was done by @Twb3:

• I removed the specific authentication variables as this is already implemented by the standard schema registry client
• I added PROTOBUFFER and JSON type
• I removed the Jsondiff stuff to rely on the pure schema registry libs
• Schemas can be embedded or in separate files
• I update graddle and groovy to ease the IDE integration (Eclipse)
• I did most of the tests I think (I did not test the schema registry connection...)
• All the registered schemas have a proper "compatibility" and do not rely on the default one
• Limitation: you cannot update the compatibility after having registered the subject
• Plan serialization is modified and I don't know why !!! ( spaces before : and dots between empty [ ])
• schemas blacklist is implemented

What should still be done in my opinion if somebody want to help:

• update documentation
• ~~add --skip-schemas command option (as for acls)~~ -> if schema registry url not provided, then schemas management skip
• add the possibility to update compatibility
• test schema registry connection options

Best, Jerome

[pfeigl]

Too bad this seemingly never made it into main sofar. Very much looking forward to this functionality