NIFI-8363 Added Single User Login Identity Provider and Authorizer

[exceptionfactory]

Description of PR

NIFI-8363 Implements a Single User LoginIdentityProvider and Authorizer as an incremental step toward a default secure standalone installation of NiFi. The LoginIdentityProvider class includes the following features:

• Reads and writes username and hashed password in login-identity-providers.xml
• Generates random username using java.util.UUID.randomUUID()
• Generates random password of using java.security.SecureRandom with Base64 encoding
• Writes generated password hash using bcrypt

The implementation is not intended for production use, but provides a basic level of security for standalone installations. Future changes will incorporate updates to default configuration files so that this implementation can be reviewed independently. Verifying runtime behavior requires the following steps:

1. Copy login-identity-providers.xml from the test resources directory to the NiFi conf directory
2. Create an authorizer definition in conf/authorizers.xml with the following elements:

<authorizer>
    <identifier>single-user-authorizer</identifier>
    <class>org.apache.nifi.authorization.single.user.SingleUserAuthorizer</class>
</authorizer>

3. Set nifi.security.user.login.identity.provider=single-user-provider in nifi.properties
4. Set nifi.security.user.authorizer=single-user-authorizer in nifi.properties
5. Set nifi.web.https.port and nifi.security keystore and truststore properties to enable HTTPS
6. Start NiFi and search nifi-app.log for Generated Username and Generated Password
7. Login with NiFi using the generated credentials

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