test: integration tests for tap-agent (#572)

* test: Enhance test coverage for tap-agent

* style: add license

* style: cargo clippy

* style: cargo fmt

* test: fix tests and cleanup

* test: remove dummy ulr

* test: fix tests

* test: removed get_grpc_url on subgraph endpoints

* test: revert trigger value typo

* test: added optional sender aggregator endpoint for sender allocation args

* test: removed get_grpc_url from unnecesary spots

* test: removed aggregator endpoint from method

* test: change unwrap_or for a match pattern obtianing url

* test: remove unused default value

Author: carlosvdr