[Documentation] Document template properties

### Relevant documentation

refarch-templates

### Problem description (optional)

For the gateway the available configuration options are documented: https://refarch.oss.muenchen.de/gateway.html#configuration
For the templates something similar is currently missing and only the `application-local.yaml` contains examples (but also not mentioned in docs).

### Desired solution

It should be documented what configuration properties are available and which are required.
Either by adding an additional section for the configuration (like for the gateway) or by making clear, that the `application-local.yaml` is the example configuration.

### Additional context (optional)

_No response_

### No duplicate

- [x] I confirm that this issue is not a duplicate

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Start with the refarch-templates documentation and inspect application-local.yaml for the configuration examples. Compare the existing gateway configuration section, then document the available and required template properties or clearly identify application-local.yaml as the example configuration; done means the properties and requirements are discoverable in the documentation.

Written by the indexing model from the issue text.