feat: add variable metadata in after and finally hooks

[suthar26]

• added variable metadata
• updated metadata and context fields to be a dataclass and json outputs
• update django app to use the local version of the sdk
• tset using the django app and hooks

[suthar26]

since we return the variable here, i am adding the featureId as a return here

[suthar26]

and Nullable string has .value property on it, if i dont add this the structure of feature_id is { value : Id }