Backend Work for Checkin Submission

[patricktownley]

• Update Mongoose Model schema to include Array of checkins

Habit model now contains an array of "Checkin" objects which can be updated each time the user submits.

• Add API method to complete a checkin for a given habit

  Currently finds by the habit's DB object id - not ideal but its a starting point.

Add functionality to checkin form …

• Basically borrowed all the concepts from the New Habit form, albeit with less validation
• Temporarily added Habit field for manual habit ID entry
• Confirmed that it can update habits on the backend

@pjconnolly12 I'm looking at you for the DB side - I think this was the Schema.

@SaraSweetie I made a bunch of changes to your Check-in form a bit in order to test that it actually worked - hopefully it's alright.

The only really wacky thing is I added a Habit ID field to the form so i could try out the below:

Obviously we will need to find a way to have state field both populated automatically and not visible to the user, or use a different field to match on.

This is my first crack at the React side of things so any and all thoughts or suggestions very welcome.

[pjconnolly12]

This looks great!

Hiding the ID should be easy, we can just store the ID in state and then grab it from there when making the POST request.

[paulywill]

@patricktownley if you would like to do the honors and click "Squash and merge" button.