Feature/bmspt 283 delegate methods

[BalintBende]

Description

PR includes the delegate callback function and stream process func for converters.

Fixes

• Link 1

Type Of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality
  to not work as expected)
• This change requires a documentation update
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no API changes)
• CI/Build related changes (so that Github is happy)
• Dockerfile related changes
• Documentation content changes
• Tests (extended coverage or fixing existing tests)
• Updated dependencies

API Changes

• Introducing a new method or property
• Updating the API
• Deprecating methods or properties

Environment (Docker)

• Adding a new environment variable
• Updating the production container

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have checked my code and corrected any misspellings
• 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
• I have tested my code in the local docker-compose environment
• My feature branch builds on Github

[github-actions]

Test Results

0 tests  ±0   0 ✅ ±0   0s ⏱️ ±0s
0 suites ±0   0 💤 ±0 
0 files   ±0   0 ❌ ±0 

Results for commit 7c099c7. ± Comparison against base commit 846135b.

♻️ This comment has been updated with latest results.

[DanielLepold]

pls consider the following solutions for the "return Task.Completed case":
if (_delegate is null) {
throw new InvalidOperationException("IBcfBuilderDelegate is not set.");
}

if (_delegate is null) {
    return Task.FromException(new InvalidOperationException("IBcfBuilderDelegate is not set."));
}

[DanielLepold]

Should the commented-out parts remain for future use?

[DanielLepold]

Awesome work!
Pls see my comments