AVRO format expected by sbt-mu-srcgen

[angoglez]

Description

Issue related: #308

When a schema is stored in compendium (.avpr format accepted by compendium, see related issue) and later we try to use the sbt-mu-srcgen plugin to obtain the .scala files (doing sbt muSrcgen) it seems it's expecting for an .avdl file.

Example output:

[error] org.apache.avro.compiler.idl.ParseException: Encountered " "{" "{ "" at line 1, column 1.
[error] Was expecting one of:
[error]     "protocol" ...
[error]     "@" ...
[error]     

Or maybe it's because the avro schema it's not properly recognized.

🔗 RELATED DOCUMENT: PART TWO - AVRO PROTOCOL (.avpr) COMPENDIUM/SBT-MU-SRCGEN MISMATCH