Add a simple cache for OAuth2 token validation

[RadovanTomik]

Negotiator pull request:

Description:

Adds a cache for userinfo and token introspection that is emptied every 5 minutes.

Checklist:

Make sure you tick all the boxes bellow if they are true or do not apply:

• I have performed a self review of my code
• My code follows Google Java Code style
• I have made my code as simple as possible
• I have added unit tests and the code coverage has not decreased
• I have updated the documentation in all relevant places

[codecov]

Codecov Report

Attention: Patch coverage is 19.04762% with 17 lines in your changes are missing coverage. Please review.

Project coverage is 76.42%. Comparing base (9fac93e) to head (8253262).

Files	Patch %	Lines
...guration/security/auth/CustomJWTAuthConverter.java	0.00%	10 Missing ⚠️
...guration/security/auth/IntrospectionValidator.java	20.00%	4 Missing ⚠️
...ator/configuration/security/auth/CacheManager.java	25.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #278      +/-   ##
============================================
- Coverage     76.84%   76.42%   -0.43%     
- Complexity      870      871       +1     
============================================
  Files           122      123       +1     
  Lines          2721     2740      +19     
  Branches        157      158       +1     
============================================
+ Hits           2091     2094       +3     
- Misses          524      540      +16     
  Partials        106      106              

Flag	Coverage Δ
unit	76.42% <19.04%> (-0.43%)	⬇️

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