Create database helper functions

[amberjones]

We need several functions to interact with our database, including but not limited to the following:

Add a user Preferences Table. 1 to 1

BOOKS

• Insert a book to the books table
• Retrieve a book from the Book Table
  Look up ISBN and return info as an object

USERS_FOLLOWERS
A look up USERS_BLOCKED needs to happen before insert

• Query for all the followers of a user (send back the usernames and IDs).
  Send back an array of objects. We will need their ID to show their "to-read" list upon clicking on their
  username client side
• Query for all users following a user (send back the usernames and IDs)

USERS_BLOCKED

• Insert User_ID and BLOCKED_ID
• ? Delete - un-block user and remove that data entry

USERS_PREFERENCE

• Insert default preferences upon user creation - reference User_ID
• Patch preference - take in User_ID
• Query for user preference. send back an object.

USERS_BOOKS

• Query for books based on boolean
• Insert book - to happen exactly after a yes or no choice is made.
• Patch - takes in User_ID and ISBN and changes Boolean