Implement ability to register as a user (back end)

[neraks]

As a web browser, I want to be able to hit a web endpoint to register as a patient user so that I can start using Record on the Go.

Acceptance criteria 1:
Given I am a web browser
When I hit this end point
Then I want to be able to send the following data:

• username (max length of 255)
• password (max length of 255)

Acceptance criteria 2:
Given I am a web browser
When I send a valid username and a valid password to the end point
Then I am added to the database as a patient.

Acceptance criteria 3:
Given I am a web browser
When I send an invalid username or invalid password to the end point
Then I am not added to the database
And Then I receive an error response

Invalid username password criteria:

• Longer than 255 characters (both)
• Username is not alpha numeric

Acceptance criteria 4:
Given I am a web browser
When I send my username and password to the end point
Then my data is secure.