UX Bug: fix confusing responses to incoming messages

Bug symptoms

• when responses disabled and i am a unsubscribed random person:
  • sending HELP (like error message in current implementation prompts me to), returns undefined
  • sending INFO triggers unauthorized message (unlike sending some normal text like "foo"), this should also probably prompt me to join
• when responses disabled and i am a subscriber:
  • the error message assumes i was trying send a command, and tells me it didn't understand my command
  • but maybe i think responses are enabled...
  • this message should include context about how nothing happened to my message because i'm not an admin (and let me know that admins could enable responses if i ask them to)
• when responses disabled and i am a random person:
  • sending non-command text (ie: misspelled command "HOLAA"), responds with "i didn't understand that" but it should prompt me to join
• when responses enabled, subscriber sending response gets oddly formatted message
  • too many line breaks and indents on second sentence

Desired Behavior

GIVEN an UNSUBSCRIBED user sending to a channel with RESPONSES ON:

• WHEN user sends HELP or INFO
  • THEN user receives the appropriate command response
• WHEN user sends any other command
  • THEN user receives Your message could not be processed because you are not subscribed to this channel. Send HELLO to subscribe.
• WHEN user sends any non-command
  • THEN user receives Your message was anonymously forwarded to the admins of ___. Please include your phone number if you want admins to respond to you. You can also send HELP to list valid commands.

GIVEN a SUBSCRIBED user sending to a channel with RESPONSES ON:

• WHEN user sends a command that they are authorized to send
  • THEN user receives appropriate command response
• WHEN user sends a command that only admins can send
  • THEN user receives a message that says Sorry, only admins can issue that command. Send HELP to see valid commands.
• WHEN user sends a non-command
  • THEN user receives Your message was anonymously forwarded to the admins of ___. Please include your phone number if you want admins to respond to you. You can also send HELP to list valid commands.

GIVEN an UNSUBSCRIBED user sending to a channel with RESPONSES OFF:

• WHEN user sends HELP or INFO
  • THEN user receives the appropriate command response
• WHEN user sends any other message (including all other commands)
  • THEN user receives Sorry, incoming messages are not enabled on this channel. Send HELLO to subscribe to announcements.

GIVEN a SUBSCRIBED user sending to a channel with RESPONSES OFF:

• WHEN user sends a valid command
  • THEN user receives appropriate command response
• WHEN user sends a non-command message
  • THEN user receives Sorry, incoming messages are not enabled on this channel. Send HELP to list valid commands.