feat: remote embeddings

[vansangpfiev]

Describe Your Changes

This pull request introduces several changes to the RemoteEngine class in the engine/extensions/remote-engine/remote_engine.cc file, primarily focusing on refactoring and adding support for embeddings. The key modifications include the introduction of a new RequestType enum, replacing hardcoded strings with constants, and refactoring functions to handle different request types.

Refactoring and Constants:

• Added constants kChatCompletions and kEmbeddings to replace hardcoded strings for request types. (engine/extensions/remote-engine/remote_engine.cc)
• Replaced hardcoded strings with kChatCompletions in various locations to improve code readability and maintainability. (engine/extensions/remote-engine/remote_engine.cc) [1] [2] [3] [4]

Function Refactoring:

• Refactored MakeChatCompletionRequest to MakeNonStreamRequest to handle both chat completions and embeddings based on the new RequestType enum. (engine/extensions/remote-engine/remote_engine.cc) [1] [2]
• Updated HandleChatCompletion to use the refactored MakeNonStreamRequest function. (engine/extensions/remote-engine/remote_engine.cc)

Embeddings Support:

• Added handling for embedding requests and responses, including new templates and URLs for embeddings. (engine/extensions/remote-engine/remote_engine.cc) [1] [2]
• Introduced new member variables embed_req_template_, embed_res_template_, and embed_url_ to store embedding-specific configurations. (engine/extensions/remote-engine/remote_engine.h)

Error Handling and Logging:

• Enhanced error handling and logging for missing required fields and template rendering errors in HandleEmbedding. (engine/extensions/remote-engine/remote_engine.cc)

These changes improve the code structure, readability, and extend the functionality of the RemoteEngine class to support embeddings alongside chat completions.

Fixes Issues

• Remote engine: Adds support for generating embeddings, empowering clients to leverage this powerful feature for tasks like semantic search and clustering. #2088

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed