Add input/output/config endpoints to server and test out configurability of runnables

[eyurtsev]

Code is in a working state. Potentially some minor kinks. Dependent on features on master, so should not be landed prior to master being released

[eyurtsev]

  File "/home/eugene/.pyenv/versions/langchain_3_9b/lib/python3.9/site-packages/starlette/routing.py", line 66, in app                                                                        
    response = await func(request)                                                             
  File "/home/eugene/.pyenv/versions/langchain_3_9b/lib/python3.9/site-packages/fastapi/routing.py", line 263, in app
    solved_result = await solve_dependencies(                                                                                                                                                 
  File "/home/eugene/.pyenv/versions/langchain_3_9b/lib/python3.9/site-packages/fastapi/dependencies/utils.py", line 612, in solve_dependencies                                               
    ) = await request_body_to_args(  # body_params checked above                               
  File "/home/eugene/.pyenv/versions/langchain_3_9b/lib/python3.9/site-packages/fastapi/dependencies/utils.py", line 742, in request_body_to_args                                             
    v_, errors_ = field.validate(value, values, loc=loc)                     
  File "pydantic/fields.py", line 884, in pydantic.fields.ModelField.validate                                                                                                                 
  File "pydantic/fields.py", line 1101, in pydantic.fields.ModelField._validate_singleton      
  File "pydantic/fields.py", line 1157, in pydantic.fields.ModelField._apply_validators
  File "pydantic/class_validators.py", line 337, in pydantic.class_validators._generic_validator_basic.lambda13                                                                               
  File "pydantic/main.py", line 711, in pydantic.main.BaseModel.validate                       
  File "pydantic/main.py", line 339, in pydantic.main.BaseModel.__init__                                                                                                                      
  File "pydantic/main.py", line 1076, in pydantic.main.validate_model                          
  File "pydantic/fields.py", line 884, in pydantic.fields.ModelField.validate                                                                                                                 
  File "pydantic/fields.py", line 1101, in pydantic.fields.ModelField._validate_singleton
  File "pydantic/fields.py", line 1157, in pydantic.fields.ModelField._apply_validators                                                                                                       
  File "pydantic/class_validators.py", line 337, in pydantic.class_validators._generic_validator_basic.lambda13                                                                               
  File "pydantic/validators.py", line 632, in pydantic.validators.make_typeddict_validator.typeddict_validator                   
  File "pydantic/main.py", line 526, in pydantic.main.BaseModel.parse_obj       
  File "pydantic/main.py", line 339, in pydantic.main.BaseModel.__init__                                                                                                                      
  File "pydantic/main.py", line 1076, in pydantic.main.validate_model                          
  File "pydantic/fields.py", line 860, in pydantic.fields.ModelField.validate                                                                                                                 
pydantic.errors.ConfigError: field "configurable" not yet prepared so type is still a ForwardRef, you might need to call RunnableConfig.update_forward_refs().                                
gi^CINFO:     Shutting down                                                                                                                                                        ```

Havne't figured out how to resolve yet