* feat - allow tagging vertex JS SDK request
* add unit testing for passing headers for pass through endpoints
* fix allow using vertex_ai as the primary way for pass through vertex endpoints
* docs on vertex js pass tags
* add e2e test for vertex pass through with spend tags
* add e2e tests for streaming vertex JS with tags
* fix vertex ai testing
* stash gemini JS test
* add vertex js sdj example
* handle vertex pass through separately
* tes vertex JS sdk
* fix vertex_proxy_route
* use PassThroughStreamingHandler
* fix PassThroughStreamingHandler
* use common _create_vertex_response_logging_payload_for_generate_content
* test vertex js
* add working vertex jest tests
* move basic bass through test
* use good name for test
* test vertex
* test_chunk_processor_yields_raw_bytes
* unit tests for streaming
* test_convert_raw_bytes_to_str_lines
* run unit tests 1st
* simplify local
* docs add usage example for js
* use get_litellm_virtual_key
* add unit tests for vertex pass through
