Custom deserializer for avro raw format

[bgranvea]

This PR implements #833.

It allows the decoding of Avro raw binary format, with a mapping configuration similar to what already exists for Protobuf, for example:

        akhq:
          connections:
            my-cluster:
              deserialization:
                avro-raw:
                  schemas-folder: "/app/avro_schemas"
                  topics-mapping:
                    - topic-regex: "data.*"
                      value-schema-file: "Schema.avsc"

A couple of remarks regarding this PR:

• it only addresses Avro "raw" binary format, that is objects encoded with low-level DatumWriter (no header), which is my use case. It could be extended to support single-object encoding (https://avro.apache.org/docs/current/spec.html#single_object_encoding) and it could also be interesting to decode object container files (https://avro.apache.org/docs/current/spec.html#Object+Container+Files) which embed the schema
• there is no support for schema referencing another schemas
• I'm not a Gradle specialist but I didn't manage to have Avro schemas used for unit tests that are compiled by Gradle Avro plugin as well as also packaged as resources, so I ended up duplicating the files...
• I modified AvroDeserializer so that displayed JSON keeps the same field order than Avro schema. This is convenient for unit tests and I think it is also for the user

[tchiotludo]

@bgranvea for that !
There is some falling test, can you look at please ? thanks 👍

[bgranvea]

Sorry for that, it was difficult to setup my dev environment, unit tests don't seem to work at all on Windows (some weird Kafka errors), I finally managed to get it work with WSL.

I fixed most of the unit tests, but there is still one failing test. I don't understand because I have the same error when I switch to the dev branch so this doesn't seem to be related to my PR. Any idea?

  org.akhq.controllers.SchemaControllerTest

    ✔ deleteNotExistApi()
    ✔ crud()
    ✘ listApi()

      org.opentest4j.AssertionFailedError: expected: <5> but was: <3>
          at org.junit.jupiter.api.AssertionUtils.fail(AssertionUtils.java:55)
          at org.junit.jupiter.api.AssertionUtils.failNotEqual(AssertionUtils.java:62)
          at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:150)
          at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:145)
          at org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:510)
          at org.akhq.controllers.SchemaControllerTest.listApi(SchemaControllerTest.java:35)

I also noticed this in Record:

    @JsonIgnore
    private SchemaRegistryClient client;

    private ProtobufToJsonDeserializer protobufToJsonDeserializer;

Shouldn't this field also be annotated with JsonIgnore?

[tchiotludo]

Test are now working, I have some flakky test I never found a way to fix.
That for pointing the missing @JsonIgnore 👍 it's fixed on dev branch.

All seems to be good, just please add some documentation on the README.md about this feature and I will merged that one

Thanks for all 👍