refactor(connectors): Add @Operation based SDK docs.

[sbuettner]

Refine and simplify SDK docs in general

Relates to https://github.com/camunda/team-connectors/issues/1096

Description

When should this change go live?

• This is already available but undocumented and should be released within a week. (add available & undocumented label)

PR Checklist

• The commit history of this PR is cleaned up, using {type}(scope): {description} commit message(s)

• My changes are for an upcoming minor release and are in the /docs directory (version 8.9).
• My changes are for an already released minor and are in a /versioned_docs directory.

• I added a DRI, team, or delegate as a reviewer for technical accuracy and grammar/style:
  • Engineering team review
  • Technical writer review via @camunda/tech-writers unless working with an embedded writer.

[github-actions]

👋 🤖 🤔 Hello, @sbuettner! Did you make your changes in all the right places?

These files were changed only in docs/. You might want to duplicate these changes in versioned_docs/version-8.8/.

• docs/components/connectors/custom-built-connectors/connector-sdk.md

You may have done this intentionally, but we wanted to point it out in case you didn't. You can read more about the versioning within our docs in our documentation guidelines.