Creates a Plug.Conn struct for testing purposes. To add additional information to the Plug.Conn struct. Use below "put" functions.

Parameter:

- method: Atom indicating the method of request.
- path: String representing the request path

Returns: Plug.Conn

Put body parameter into a Plug.Conn. Only for testing purposes

Put arbitary data in Plug.Conn struct under given key.

Parmeter:

- conn: Plug.Conn struct
- key: Atom indicating the place where to put the data in
- value: Any value to be put in Plug.Conn

Returns: Plug.Conn

Put query params into Plug.Conn. Only for testing purposes