Certification (skr-common 0.1.3 API)

```
public interface Certification
```
Certification to identify a user. e.g.
- username + password
- phone + sms captcha
- email + captcha
- OAuth

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`java.lang.String`	`getIdentity()`	identity for this Certification, e.g.
`java.lang.String`	`getUserPrincipalIdentity()`	identity for the user principle that this certification is binding to, e.g.

- Method Detail
  - getIdentity
```
java.lang.String getIdentity()
```
    identity for this Certification, e.g. username, phone number, email address, etc.
  - getUserPrincipalIdentity
```
java.lang.String getUserPrincipalIdentity()
```
    identity for the user principle that this certification is binding to, e.g. account.id / user.id