KNOX-2713 - Allowing end-users to customize 'user limit exceeded' action when creating Knox tokens

[smolnar82]

What changes were proposed in this pull request?

Changing Knox's default behavior when a user exceeds the configured token limit: if REMOVE_OLDEST is configured, Knox will remove the oldest token instead of returning an error.

How was this patch tested?

Updated existing JUnit tests as well as added new ones:

$ mvn clean -Dshellcheck=true verify -Prelease,package -am -pl gateway-service-knoxtoken
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  05:56 min
[INFO] Finished at: 2022-03-04T15:23:36+01:00
[INFO] ------------------------------------------------------------------------

Manual testing:

• set gateway.knox.token.limit.per.user = 1 in gateway-site.xml
• set knox.token.user.limit.exceeded.action = REMOVE_OLDEST in the homepage topology for the KNOXTOKEN service
• restarted Knox and created a token with comment token 1 on the Token Generation page
• created another token with comment token 2 successfully (and the previously created one got revoked):

2022-03-04 15:30:48,390 3ee2f801-ed84-4cee-bf9d-8da686266eed ERROR service.knoxtoken (TokenResource.java:getAuthenticationToken(669)) - Unable to get token for user admin: token limit exceeded
2022-03-04 15:30:48,391 3ee2f801-ed84-4cee-bf9d-8da686266eed INFO  service.knoxtoken (TokenResource.java:getAuthenticationToken(675)) - Revoking admin's oldest token 066b2c...2bb6f5 ...
2022-03-04 15:30:48,407 3ee2f801-ed84-4cee-bf9d-8da686266eed INFO  service.knoxtoken (TokenResource.java:revoke(512)) - Knox Token service (homepage) revoked token 066b2c...2bb6f5 (066b2cc3...946c6e2bb6f5) (renewer=admin)
2022-03-04 15:30:48,413 3ee2f801-ed84-4cee-bf9d-8da686266eed INFO  service.knoxtoken (TokenResource.java:getAuthenticationToken(704)) - Knox Token service (homepage) issued token eyJqa3...k1ikvg (893cbbef...a754c8a4f5bb)