docs: add local stack examples

[patlo-iog]

Description:

Open for feedback. Experiment with local examples with generated docker configurations.

https://nickel-lang.org/ is used to generate all compose.yaml in each example.

example	description
st	single-tenant configuration without external services (except database)
st-multi	3 instances of single-tenant configuration
st-vault	single-tenant with Vault for secret storage
mt	multi-tenant configuration using built-in IAM
mt-keycloak	multi-tenant configuration using Keycloak for IAM
mt-keycloak-vault	multi-tenant configuration using Keycloak and Vault

Example we might consider in the future

• vault with file storage
• vault with AppRole authentication
• keycloak with agent admin role
• oidc4vc configuration
• overriding config with application.conf
• production?

Checklist:

• My PR follows the contribution guidelines of this project
• My PR is free of third-party dependencies that don't comply with the Allowlist
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked the PR title to follow the conventional commit specification

[github-actions]

Integration Test Results

13 files  ±0  13 suites  ±0   2s ⏱️ ±0s
29 tests ±0  29 ✅ ±0  0 💤 ±0  0 ❌ ±0 
32 runs  ±0  32 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 458d0ce. ± Comparison against base commit 16bc10d.

♻️ This comment has been updated with latest results.

[github-actions]

Unit Test Results

 90 files  ±0   90 suites  ±0   21m 9s ⏱️ -28s
776 tests ±0  768 ✅ ±0  8 💤 ±0  0 ❌ ±0 
783 runs  ±0  775 ✅ ±0  8 💤 ±0  0 ❌ ±0 

Results for commit 458d0ce. ± Comparison against base commit 16bc10d.

♻️ This comment has been updated with latest results.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud