Create a custom endpoint for generate a Direct Line token

[MrDave1999]

It is necessary to create an endpoint that is responsible for calling the DirectLine API to generate a token and this is because if it is done from the client, the secret key would be exposed, this brings as a consequence that any malicious user could access any conversation associated with the bot.

The solution is to create a service on the back-end side in which it is in charge of making a request to the next endpoint:

POST https://directline.botframework.com/v3/directline/tokens/generate
Authorization: Bearer SECRET_KEY

This can be done on the front-end side but it would be insecure.