Disable database distributed cache in non-self-hosted environments

[brant-livefront]

📔 Objective

As we expand usage of distributed caching, we discovered that the redis connection string is not enabled in all of our environments / containers. The current code defaults to a database-backed distributed cache if the Redis string is not available. While this is a sensible backup for self-hosted environments, it does not work well in the cloud environment.

This PR adds a check to ensure that self-hosted is true before adding the database distributed cache. In cloud, this will now add nothing. This is an acceptable outcome for cloud. The ExtendedCache service collection extension is calling TryWithRegisteredKeyedDistributedCache if the redis connection string is not set. This means that it will fail gracefully if there is no defined distributed cache - falling back to simply caching in memory (L1).

See the section in ExtendedCacheServiceCollectionExtensions.cs that starts at line 126 for more detail around this scenario. There's also a test: ExtendedCacheServiceCollectionExtensionsTests.AddExtendedCache_NoDistributedCacheRegistered_WorksWithMemoryOnly that explicitly tests for this scenario.

⏰ Reminders before review

• Contributor guidelines followed
• All formatters and local linters executed and passed
• Written new unit and / or integration tests where applicable
• Protected functional changes with optionality (feature flags)
• Used internationalization (i18n) for all UI strings
• CI builds passed
• Communicated to DevOps any deployment requirements
• Updated any necessary documentation (Confluence, contributing docs) or informed the documentation team

🦮 Reviewer guidelines

• 👍 (:+1:) or similar for great changes
• 📝 (:memo:) or ℹ️ (:information_source:) for notes or general info
• ❓ (:question:) for questions
• 🤔 (:thinking:) or 💭 (:thought_balloon:) for more open inquiry that's not quite a confirmed issue and could potentially benefit from discussion
• 🎨 (:art:) for suggestions / improvements
• ❌ (:x:) or ⚠️ (:warning:) for more significant problems or concerns needing attention
• 🌱 (:seedling:) or ♻️ (:recycle:) for future improvements or indications of technical debt
• ⛏ (:pick:) for minor or nitpick changes

[github-actions]

Checkmarx One – Scan Summary & Details – 5dbf768d-2acf-4d88-a2af-32fcfbc845bf

Great job! No new security vulnerabilities introduced in this pull request

[withinfocus]

I thought it was transient, but there are test failures given cache resolution now.

[codecov]

Codecov Report

❌ Patch coverage is 7.14286% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.72%. Comparing base (f82552f) to head (776787f).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...SharedWeb/Utilities/ServiceCollectionExtensions.cs	7.14%	12 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6783      +/-   ##
==========================================
- Coverage   54.84%   54.72%   -0.12%     
==========================================
  Files        1920     1920              
  Lines       85255    85261       +6     
  Branches     7633     7634       +1     
==========================================
- Hits        46757    46659      -98     
- Misses      36718    36830     +112     
+ Partials     1780     1772       -8     

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[withinfocus]

I don't foresee this to ever be used in practice for our cloud but it can be in place for fallbacks when configs don't exist as expected.