Organize sections into a repositories chapter within navigation.

[gemmaro]

• You have read the Spring Data contribution guidelines.
  • > Make sure you provide your full name and an email address registered with your GitHub account. All commits must include a Signed-off-by trailer at the end of each commit message to indicate that the contributor agrees to the Developer Certificate of Origin.
• You use the code formatters provided here and have them applied to your changes. Don’t submit any formatting related changes.
  • There is no code changes.
• You submit test cases (unit or integration tests) that back your changes.
  • There is no code changes.
• You added yourself as author in the headers of the classes you touched. Amend the date range in the Apache license header if needed. For new types, add the license header (copy from another file and set the current year only).
  • There is no code changes.

Hello,

This is a modification to add a "Repositories" chapter to the navigation.
Currently, at the beginning of the JPA chapter, there is a link to "Working with Spring Data Repositories".
However, since this page is not in the navigation, readers might not know where to go next.
Therefore, I have organized the sections related to repositories into a single chapter.

Thank you.

[mp911de]

The structure of JPA is very different from e.g. MongoDB as JPA doesn't have a general section. With the Antora-based navigation we intentionally merged the Commons-part with the store-specific one as previously that split has caused quite some confusion.

That being said, if you have ideas about refining the structuring while keeping the merged approach, feel free to rework your pull request.