Module .csproj references *.Contracts but injects services from impl assembly, causing opaque DI failures

[antosubash]

Several modules declare ProjectReference to peer modules' *.Contracts projects only, but their endpoints inject services implemented in the peer's main assembly. When a downstream app installs the module without the peer's runtime package, startup fails with a misleading error.

Concrete failures (consuming 0.0.34 from a fresh Microsoft.NET.Sdk.Web host)

Admin → OpenIddict. SimpleModule.Admin.csproj references SimpleModule.OpenIddict.Contracts only, but Endpoints/Admin/AdminSessionsEndpoint.cs injects IOpenIddictSessionContracts (implementation lives in SimpleModule.OpenIddict). Without the OpenIddict package installed, host crashes at startup with:

System.InvalidOperationException: Body was inferred but the method does not allow inferred body parameters.
Parameter           | Source
---------------------------------
id                  | Route (Inferred)
tokenId             | Route (Inferred)
sessionContracts    | Body (Inferred)

Minimal-API misclassifies the unresolved DI parameter as body-bound. The actual problem (missing service registration) is invisible.

Email → BackgroundJobs. SimpleModule.Email requires IBackgroundJobs from SimpleModule.BackgroundJobs for EmailService and RetryFailedEmailsJob but doesn't declare the dependency. Same opaque failure mode.

Fix

For each module that injects services from a peer at runtime, declare a PackageReference (not just *.Contracts) so NuGet pulls the impl transitively. Alternatively, add a startup validator (see related issue) that emits "ModuleX requires ModuleY to be installed" before the DI container is built.