`B`: Integrate the chain "invoke" functionality into `ConfigurationsAPI`

[Siddharth-Khattar]

Chain Invoke with Configuration

(continue after #20 )

Triggered when the user clicks Run after a Configuration has been provided

New Configuration DTO

A configuration must now represent the chain runnable-attribute pairs as well as their specific configurable_params

Create a new Configuration schema that represents the new structure for the AttributeName:Runnable pair in the Chain where each runnable is having its own set of configurable_params. Idea for the schema shape:

1. The attribute_name : Runnable K-V pairs (that are using "configurable_fields" and co.) as a dict.
2. The extracted corresponding constants/fields/params (along with the default values provided) that actually are configurable for each of those K-V pairs

New Configurations endpoints (CR UD)

Store the the config data specified in request body in the DB and then invoke the chain with it. Steps:

1. POST the configuration provided in the request body in DB as a new Configuration for that Session -> returns ConfigId
2. Create a chain invoke engine that calls batch function with the specified configuration params for each question (GET questions)
3. POST the Answers generated for that specific configId in DB
4. Expose (GET) all the available configurations for the frontend to read