Add support for RubyLLM::Message Content

[aniamisiorek]

Currently, when using RubyLLM as the LLM client, openllmetry throws an error (undefined method 'has_key?' for an instance of RubyLLM::Message) when attempting to log the response. RubyLLM uses the message object, which can be seen here:

Response object: #<RubyLLM::Message:0x00000001350b08c0 @role=:assistant, 
@content=#<RubyLLM::Content:0x00000001321134c8 @text="{\"action\":\"NONE\"}", @attachments=[]>, 
@tool_calls=nil, @input_tokens=958, @output_tokens=9, @model_id="claude-3-5-sonnet-20240620", @tool_call_id=nil>

The source code also appears here:
https://github.com/crmne/ruby_llm/blob/e7521c98a5c39ca8ad79b9d0f2a9d74efc67535c/lib/ruby_llm/message.rb#L7

[nirga]

Thanks for reporting @aniamisiorek and sorry we missed this!
We'll work on a fix if it's still relevant :)