[MISC] Mailing List Backend Route

[mraysu]

We will want to maintain a mailing list for users who would like to be involved in the regular newsletter being posted by HoMEwork. To do so, we will be creating documents for each email subscribed.

For your PR

1. Create a mongodb schema that contains the following fields:

• name (contact's full name)
• email (valid email string)

2. Create the Following Routes

POST api/subscriptions/create - adds an email to the database. Ensure the email is a valid email and is not already on the subscription list.

GET api/subscriptions - request a list of all subscriptions

DELETE api/subscription - removes a subscription from the database, querying using the email string. Validate the email before querying.