Use Cases refactoring

[undavide]

Description

Over time, the Use Cases page has become too large; it's been split into a sub-menu, grouping cases by subject and moving them to individual pages. This not only rationalises and makes the content more accessible but also allows adding additional content in the future—à la cookbook—to cover new APIs with mixed material (narrative/snippets) that is not too long (tutorials) and not too short (just code).

The submenus ATM are:

• Content Management
• Authentication and Authorization
• Client-side Data
• User Interaction
• Environment Settings
• Monetization Flows
• Content Authoring and Metadata

Old links pointing to the single use_cases.md page have been chased all over the doc website and redirected to the new pages. I've fixed some internal links that were expressed as https:// URLs. The original content has also been touched, lightly, for clarity.

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[hollyschinsky]

LGTM!