Add domain linkage grpc

[wulfraem]

Description of change

Adds domain linkage validation to gRPC bindings.

Four endpoints are added. Validation can be started from domain or DID, pre-fetched did-configuration.json files can be pased to endpoints on separate endpoints for domain and DID, looling like following:

• domain_linkage/DomainLinkage.validate_domain
• domain_linkage/DomainLinkage.validate_domain_against_did_configuration
• domain_linkage/DomainLinkage.validate_did
• domain_linkage/DomainLinkage.validate_did_against_did_configurations

Links to any relevant issues

• fixes Implement Domain Linkage #1323 (subtask of [Task] Implement experimental gRPC binding #1272)

Type of change

• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Fix

How the change has been tested

Added integration tests for domain linkage validation when starting with domain and DID. did-configuration.json files are passed to endpoint in these tests and not fetched from server.

Change checklist

Add an x to the boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• 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
• 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

[UMR1352]

Congrats on submitting your very first PR! Very well done!