[docs] Expand 13.2 Connection property suffix breaking change with migration guidance

[IEvangelist]

Summary

Fixes #413.

The Connection property suffix breaking change in the Aspire 13.2 release notes currently reads, in its entirety:

A connection property suffix has been added which may require updates to code that accesses connection properties directly.

That leaves readers — particularly anyone upgrading directly from 13.0 to 13.2 — without enough detail to actually migrate. This PR expands the section into a full migration guide.

Changes

In src/frontend/src/content/docs/whats-new/aspire-13-2.mdx (### Connection property suffix):

• Replace the one-sentence stub with an explanation of the rename pattern: properties whose value is the name of a sub-entity now end with Name.
• Add a canonical table grouped by rename, covering all 15 affected resource types:
  • Database → DatabaseName across the 10 SQL/NoSQL/Azure database resources.
  • Model → ModelName for AzureOpenAIDeploymentResource, OpenAIModelResource, GitHubModelResource, and FoundryDeploymentResource.
  • ConsumerGroup → ConsumerGroupName for AzureEventHubConsumerGroupResource.
• Add before/after environment variable examples (Postgres APPDB_DATABASE → APPDB_DATABASENAME, OpenAI CHAT_MODEL → CHAT_MODELNAME, Event Hubs ORDERS_CG_CONSUMERGROUP → ORDERS_CG_CONSUMERGROUPNAME).
• Add before/after C# AppHost examples for GetConnectionProperty(...) callers.
• Add a migration checklist ("Identify affected code") covering AppHost calls, env-var consumers in Python/JS/Go apps, and custom Bicep/Helm templates — plus a positive note that C# apps using the standard Aspire client integrations don't need source changes.
• Add a <Aside type="note"> that cross-links to the partial table on the 13.1 page and clarifies that apps already on 13.1.x use the new names today.

The heading text is unchanged so the anchor #connection-property-suffix remains stable for external links.

Evidence the issue still reproduces

Verified against the live site at https://aspire.dev/whats-new/aspire-13-2/#connection-property-suffix on the day this PR was opened. The Connection property suffix section under ⚠️ Breaking changes renders only the single sentence quoted in the Summary, with no table, no code samples, and no migration steps — in contrast to the AIFoundry to Foundry transition section immediately below it, which has prose, an XML snippet, and a C# migration example.

The screenshot used for verification is in the session workspace (live-stub.png) and shows the rendered section.

Sources for the rename table

The renames in the table are confirmed against the current microsoft/aspire main:

• Database → DatabaseName is yielded from GetConnectionProperties() in src/Aspire.Hosting.PostgreSQL/PostgresDatabaseResource.cs, src/Aspire.Hosting.MySql/MySqlDatabaseResource.cs, src/Aspire.Hosting.SqlServer/SqlServerDatabaseResource.cs, src/Aspire.Hosting.Oracle/OracleDatabaseResource.cs, src/Aspire.Hosting.MongoDB/MongoDBDatabaseResource.cs, src/Aspire.Hosting.Milvus/MilvusDatabaseResource.cs, src/Aspire.Hosting.Azure.Sql/AzureSqlDatabaseResource.cs, src/Aspire.Hosting.Azure.CosmosDB/AzureCosmosDBDatabaseResource.cs, src/Aspire.Hosting.Azure.PostgreSQL/AzurePostgresFlexibleServerDatabaseResource.cs, and src/Aspire.Hosting.Azure.Kusto/AzureKustoReadWriteDatabaseResource.cs.
• Model → ModelName in src/Aspire.Hosting.Azure.CognitiveServices/AzureOpenAIDeploymentResource.cs, src/Aspire.Hosting.OpenAI/OpenAIModelResource.cs, src/Aspire.Hosting.GitHub.Models/GitHubModelResource.cs, and src/Aspire.Hosting.Foundry/FoundryDeploymentResource.cs.
• ConsumerGroup → ConsumerGroupName in src/Aspire.Hosting.Azure.EventHubs/AzureEventHubConsumerGroupResource.cs.

The rename first shipped in 13.1.0 via microsoft/aspire#13471 (commit ff437b1f7 on main, backport d6668f526 to release/13.1). The 13.2 changelog calls it out separately for the benefit of apps that skip 13.1.

The environment-variable projection rule ([RESOURCE]_[PROPERTY] uppercased, hyphens and dots replaced with underscores) is implemented in SplatConnectionProperties and EnvironmentVariableNameEncoder.Encode in microsoft/aspire.

The AuthenticationDatabase → AuthenticationDatabaseName and Organization → OrganizationName renames mentioned in PR #13471's description are intentionally not listed in the table — those keys are still emitted unchanged on main (MongoDBServerResource.cs still yields "AuthenticationDatabase"; GitHubModelResource.cs still yields "Organization").

How I verified

1. Re-read the issue body and the live whats-new/aspire-13-2 page with Playwright to confirm the breaking-change section is still a stub.
2. Grepped microsoft/aspire main for every "DatabaseName", "ModelName", and "ConsumerGroupName" GetConnectionProperties() yield site to confirm the rename table.
3. Confirmed the WithEnvironment(string, ReferenceExpression), GetConnectionProperty(IResourceWithConnectionString, string), and ReferenceEnvironmentInjectionFlags.ConnectionProperties API surface used in the new code samples is still public on main.
4. Verified the cross-reference link /whats-new/aspire-13-1/#connection-properties-rename resolves: the heading exists at src/frontend/src/content/docs/whats-new/aspire-13-1.mdx:579 (### Connection Properties rename) and slugifies to that anchor.
5. Kept the heading text Connection property suffix unchanged so #connection-property-suffix continues to resolve.

To reproduce locally:

gh issue view 413 --repo microsoft/aspire.dev
git fetch upstream
git checkout dapine/connection-property-suffix-413
cd src/frontend
npm install
npm run dev
# Open http://localhost:4321/whats-new/aspire-13-2/#connection-property-suffix

Scope and out-of-scope

• Touches only src/frontend/src/content/docs/whats-new/aspire-13-2.mdx.
• The partial table in whats-new/aspire-13-1.mdx is intentionally left as-is; the 13.2 page is now the canonical reference. A follow-up could optionally cross-link or expand the 13.1 table — happy to do that in this PR if reviewers prefer.
• The Japanese translation (ja/whats-new/aspire-13-2.mdx) is left to the regular translation workflow.
• The product-repo spec docs/specs/connection-properties.md in microsoft/aspire still uses the old key names. That's outside this docs PR's scope.