What changes did you make? (Give an overview)

Added new cluster property "gcpSchemaRegistry" to enable compatibility with new GCP Schema Registries.
This property can be used in config.yaml file like this:

kafka:
  clusters:
    - name: local  # Unique name identifier for the Kafka cluster
      bootstrap-servers: kafka1:9092,kafka2:9092  # List of Kafka broker addresses

      schemaRegistry: https://managedkafka.googleapis.com/v1/projects/PROJECT_ID/locations/REGION/schemaRegistries/REGISTRY_ID
      gcpSchemaRegistry: true # false by default

Or can be enabled with the env variable: KAFKA_CLUSTERS_0_GCPSCHAMAREGISTRY=true

Important changes in code are:

• Add bearer token generation for auth with GCP Schema Registry in WebClientConfigurator
• Add custom bearer token provider in SchemaRegistrySerde
• Add the new gcpSchemaRegistry config property in kafbat-ui-api
• Add new schema fields kafka-sr-api for compatibility level as GCP Schema Registry return different format.
• Add condition to use compatibility or compatibliityLevel field based on gcpSchemaRegistry enabled or not in
  SchemaRegistryService

It's needed to use gcloud auth application-default login to get the credentials to connect to GCP Schema
Registries or run kafka-ui in a compute engine instance or GKE with a service account with the needed permissions.

Note: This functionality only works now with Avro schema types as these are the ones I work with.
It could work with Protobuf schemas, but not with JSON ones as GCP Schema Registries don't
support them.

How Has This Been Tested? (put an "x" (case-sensitive!) next to an item)

• Manually (please, describe, if necessary)

  Changes tested connecting to GCP and Confluent Schema Registries to check:

  • All Schemas registered are shown in Schema Registry dashboard
  • Topic events are deserialized correctly in the topics dashboards.

  It was impossible to pass unit tests even before adding any change :'(

Checklist (put an "x" (case-sensitive!) next to all the items, otherwise the build will fail)

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (e.g. ENVIRONMENT VARIABLES)
• My changes generate no new warnings (e.g. Sonar is happy)
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

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