fix: Error codes needs to be documented in Swagger

[William-Hill]

Fixes #576

Agent Summary

/openapi.go to the chat.
Added pkg/pipeline/errors.go to the chat.
Added pkg/pipeline/service.go to the chat.
Added proto/api/v1/api.pb.gw.go to the chat.
Added proto/api/v1/api.proto to the chat.

Makefile

cmd/conduit/main.go

pkg/connector/errors.go

proto/api/v1/api.pb.go

proto/api/v1/api_grpc.pb.go

https://github.com/conduitio/conduit
Scraping https://github.com/conduitio/conduit...

http://localhost:8080/v1/connectors
Scraping http://localhost:8080/v1/connectors...
HTTP error occurred: [Errno 61] Connection refused
Failed to retrieve content from http://localhost:8080/v1/connectors

http://localhost:8080/openapi/#/`)
Scraping http://localhost:8080/openapi/#/`)...
HTTP error occurred: [Errno 61] Connection refused
Failed to retrieve content from http://localhost:8080/openapi/#/`)

https://github.com/ConduitIO/conduit/blob/main/LICENSE.md
Scraping https://github.com/ConduitIO/conduit/blob/main/LICENSE.md...

http://localhost:8080/v1/pipelines/<pipeline_id>/start
Scraping http://localhost:8080/v1/pipelines/<pipeline_id>/start...
HTTP error occurred: [Errno 61] Connection refused
Failed to retrieve content from
http://localhost:8080/v1/pipelines/<pipeline_id>/start
Initial repo scan can be slow in larger repos, but only happens once.
Your estimated chat context of 215,195 tokens exceeds the 65,536 token limit for
openrouter/deepseek/deepseek-chat!
To reduce the chat context:

• Use /drop to remove unneeded files from the chat
• Use /clear to clear the chat history
• Break your code into smaller files
  It's probably safe to try and send the request, most providers won't charge if
  the context limit is exceeded.
  litellm.BadRequestError: OpenrouterException - {"error":{"message":"This
  endpoint's maximum context length is 163840 tokens. However, you requested about
  188362 tokens (188362 of text input). Please reduce the length of either one, or
  use the context-compression plugin to compress your prompt
  automatically.","code":400,"metadata":{"provider_name":null}},"user_id":"user_3C
  EeCGEy5UD03LA5fyj9Xe8qgTU"}

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Generated by conduit-agent-experiment (archivist: Gemini Flash, implementer: openrouter/deepseek/deepseek-chat, 1 iterations).