Login using National Provider Identifier

[kiteena]

Description:
As a doctor, I want to be able to log into the application with my NPI number and a password.

Acceptance Criteria:

1. A doctor should be able to log into the application with:
   1a. NPI Identifier as Username
   1b. Password of their own choosing
2. A doctor new to the application should be prompted to set their password.
3. Upon logging into the application, the NPI should be checked as a valid NPI number using the following database https://npiregistry.cms.hhs.gov/.