[Change suggestion] Refactor client connector code

[whatvn]

Current code base relies on client connection interface to send request to Microsoft Bot API which is limit in only 2 methods:

// Client provides interface to send requests to the connector service.
type Client interface {
	Post(url url.URL, activity schema.Activity) error
	Delete(url url.URL, activity schema.Activity) error
}

Although it's enough to interact with activity, but it makes the code limit to activity usage only, we can only send and delete activity where provider API provides many other API for the bot itself.

Suggestion:

1. Client interface can be extended/modified so that it can include response in return values, client can then send request based on active activities, while still can reuse response from Microsoft to process response themself
2. Add full request method to client interface (GET, PUT), as Microsoft provides api with these method also.

Any input? I would love to submit a PR if necessary.