Add support for annotations into Schema

[zio]

Add support for annotations into Schema

[jdegoes]

I think we want to preserve the annotations in the conversion, and because individual fields can have annotations, we'll probably need to store that data in either a tuple or a wrapper data type that stores both the schema of the field as well as its (field-specific) annotations.

[jdegoes]

I think we should allow the user to attach annotations to something constructed by hand.

[thinkharderdev]

@jdegoes Going to start work on this one. A couple of questions though:

1. Do we want to preserve the annotations when going from CaseClassN -> GenericRecord (ie when calling CaseClassN.structure)? I could see where we might want to hand on to them if we use the generic representation as an intermediate encoding when do migrations between case class versions.
2. If we want to encode annotations in GenericRecord, should we allow them to be specified when manually constructing a GenericRecord