docs: describe new API concepts (#7975)

# Which Problems Are Solved

We have not enough internal and external input about our ideas for the
new API design.

# How the Problems Are Solved

We make the concepts easily accessible by publishing them in our docs
and making them concise.

# Additional Context

- Contributes to #6305
- Replaces the PR #7821 which defines protos in more detail

Only resources and settings are in the scope of this concept.
A possible solution for defining the outscoped methods could for example
look like this:

## ZITADELInsights

query services for auditing, analytics and data synchronization.

- Events
- Milestones

## ZITADELOperations

- Health
- Failed Events
- Views
- Metrics (version, uptime etc.)

docs/docusaurus.config.js

@@ -186,7 +186,7 @@ module.exports = {
       selector: "div#",
     },
     prism: {
-      additionalLanguages: ["csharp", "dart", "groovy", "regex", "java", "php", "python"],
+      additionalLanguages: ["csharp", "dart", "groovy", "regex", "java", "php", "python", "protobuf"],
     },
     colorMode: {
       defaultMode: "dark",