feat: Remote Secure Token Service

[wolf4ood]

What this PR changes/adds

Implements a remote version of SecureTokenService using OAuth2 client credentials flow.

Why it does that

iatp adotpion

Further notes

Additionally modules:

• identity-trust-sts-core
• identity-trust-sts-embedded

are moved into :extensions:common:iam:identity-trust:identity-trust-sts

Linked Issue(s)

Closes #3564

[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (6d8937d) 72.45% compared to head (b3e225e) 72.52%.
Report is 1 commits behind head on main.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3569      +/-   ##
==========================================
+ Coverage   72.45%   72.52%   +0.07%     
==========================================
  Files         887      891       +4     
  Lines       17846    17917      +71     
  Branches     1023     1024       +1     
==========================================
+ Hits        12930    12995      +65     
- Misses       4480     4485       +5     
- Partials      436      437       +1     

Files	Coverage Δ
...tytrust/validation/SelfIssuedIdTokenValidator.java	92.30% <ø> (-0.80%)	⬇️
...ts/controller/SecureTokenServiceApiController.java	100.00% <100.00%> (ø)
...itytrust/sts/core/StsDefaultServicesExtension.java	71.42% <ø> (ø)
...ntitytrust/sts/core/StsDefaultStoresExtension.java	66.66% <ø> (ø)
...ts/core/defaults/service/StsClientServiceImpl.java	100.00% <ø> (ø)
...ts/service/StsClientTokenGeneratorServiceImpl.java	100.00% <100.00%> (ø)
...ts/core/defaults/store/InMemoryStsClientStore.java	100.00% <ø> (ø)
...trust/sts/embedded/EmbeddedSecureTokenService.java	100.00% <100.00%> (ø)
...tytrust/sts/embedded/SelfIssuedTokenDecorator.java	100.00% <ø> (ø)
...titytrust/sts/remote/RemoteSecureTokenService.java	100.00% <100.00%> (ø)
... and 4 more

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.