Display warning about missing component/policy in config whenever possible

Description of Problem: In most instances, it is straightforward to infer from the domain file or the training data that the user is trying to use a feature that is conditional on a component/policy being included in the config.yml file.

Identifying these situations while training and displaying preemptive warnings could potentially save the user effort/time by avoiding unnecessary retraining in that case.

Overview of the Solution: Display appropriate warnings during the respective parsing steps by comparing it against the config file. It could be something along the lines of "Found usage of triggers in domain file, but could not find MappingPolicy in config.yml that is needed for it to work".

Examples (if relevant): The example that brought me here was triggers. An intent in the domain file that looks like this: - request_human: {"triggers": "action_human_handoff"} without MappingPolicy being included in config.yml. But there are many more examples.

Blockers (if relevant):

Definition of Done:

• Perform checking for policies
• Perform checking for NLU pipeline features

[akelad]

ok next time i think it’s better to have two separate issues if two separate PRs are going to fix it 😃

[btotharye]

@wochinge yep!