Implement patron PIN field instead of patron password field

Purpose/Overview:
In its current implementation SIP2 assumes that PIN are stored in the password field of the user record. Once the PIN field is available, the switch will need to accommodate following scenarios:

Scenario 1:
Given: Patron scans the library card at the kiosk
When: the scan is completed and the patron is being prompted for PIN
Then: PIN is verified against FOLIO and once confirmed patron might continue with check-out

Scenario 2:
Given: Patron enters (supported by the library) external id
When: Patron is being prompted for PIN
Then: External id is verified against FOLIO and once confirmed patron might continue with check-out

Scenario 3:
Given: Patron provides invalid identification (library card or external id)
When: credentials are checked against FOLIO
Then: Kiosk displays messages issued by FOLIO for invalid password and patron account is locked after 5 consecutive invalid entries

Scenario 4:
Given: Given the library does not require user to provide PINs for validation
When: patron scans their library card or provides external id
Then: the patron is not prompted for PIN

Additional information:
Initial implementation covered by SIP2-61. Link to the related PR: https://github.com/folio-org/edge-sip2/pull/28

Approach:
<to be filled by developer>

Acceptance criteria:

• Unit tests are written so that test coverage doesn't drop below 85%