Added support for multi-config api calls + added tests

[drazvan]

by @makeshn

Added initial support for multi_config api calls using the server API.

Changelog

nemoguardrails/rails/llm/config.py

• Overload '+' operator to add together two RailsConfig objects. ex. c = a + b. The attributes of b will overwrite attributes of a.
• Create helper function _join_rails_configs to combine two RailsConfig objects. Follows the logic of _join_config method. We have two hard checks in this function - we require the action_server_url to be the same, we require that if model_type is the same across configs, then the model_engine and model attributes must match.
• Create helper function _update_rails_config function to handle combining config.rails - FactChecking, Input, Output, SensitiveDataDetection, Retrieval. For Input, Output and Retrieval rails, we append together the flows. For the others, we check if the attributes in the UpdatedRailsConfig is set/empty. If set, it overwrites the BaseRailsConfig attribute, if empty - we just retain the BaseRailsConfig.

nemoguardrails/server/api.py

• Add config_ids field to RequestBody - List of strs.
• Modify _get_rails function to operate on list of strs. We generate a cache key to be concatenation of configs passed. The configs are combined two at a time to get the full_llm_config.
• LLMRails object is constructed from full_llm_config and used for the app.

nemoguardrails/actions/action_dispatcher.py

• Loop over all config paths and Load actions.

Signed-off-by: Makesh Narsimhan Sreedhar makeshn@nvidia.com

[drazvan]

@makeshn:

While this approach works, it adds a lot of duplication in terms of the joining logic. A RailsConfig object can be transformed into a dict using the .dict() method, and then the existing _join_config method can be used. Finally, the joined RailsConfig object can be reconstructed using RailsConfig(**joined_dict). This approach should also simplify the code significantly.