Improvement to Langchain.logger

[andreibondarev]

Is your feature request related to a problem? Please describe.

• [x] Instead of the method_missing approach, use the progname to set "[Langchain.rb]" in front of the logs.
• [x] Enable a way to output logs to a specified file path. (@dferrazm)
• [ ] Within the Langchain::LLM::* classes, make sure the different Net::HTTP, Faraday or client libraries are using the global Langchain.logger configuration.
• [x] Within the Langchain::Vectorsearch::* classes, make sure the different Net::HTTP, Faraday or client libraries are using the global Langchain.logger configuration.

[dferrazm]

• [X] Instead of the method_missing approach, use the progname to set "[Langchain.rb]" in front of the logs.
• [X] Enable a way to output logs to a specified file path.

☝️ Fixed by #796

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Within the Langchain::LLM::* classes, make sure the different Net::HTTP, Faraday or client libraries are using the global Langchain.logger configuration.

For that one ☝️ , I'll do in a different PR, since I still haven't gone through all the clients.