Introduce CoreEx.Cosmos: typed Cosmos DB data access, outbox, and Contoso.Customers sample

AGENTS.md

@@ -72,6 +72,7 @@ Rules that are easy to violate and cause real breakage or wrong choices:
 - **No AutoMapper** — do not introduce AutoMapper. All mapping is explicit via `Mapper<>` (application layer) or `BiDirectionMapper<>` (infrastructure layer).
 - **`.ConfigureAwait(false)`** — always use it in service and repository code.
 - **File-scoped namespaces** — `namespace Foo.Bar;` only; never block-scoped `namespace Foo.Bar { }`.
+- **Query materialization across data-access packages** — a new data-access package (e.g. `CoreEx.Cosmos`, a future `CoreEx.MongoDb`) should not materialize queries via `IQueryable<T>` extension methods named with a bare, generic-sounding verb (`ToListAsync`, `ToItemsResultAsync`, `ToMappedItemsAsync`, etc.) if another CoreEx package (or a third-party one, e.g. `Microsoft.EntityFrameworkCore`) already defines an identically-shaped one on the same receiver type. C# extension-method resolution has no precedence rule between two equally-applicable candidates from different namespaces — it is a hard `CS0121` ambiguous-call compile error in any file that imports both namespaces, not merely a style clash. The preferred fix is a package-owned query-wrapper type (e.g. `CoreEx.Cosmos`'s `CosmosDbQuery<TModel>`, returned from `CosmosDbContainer<TModel>.Query(...)` instead of a bare `IQueryable<TModel>`) so materializers are instance methods on that type — a different receiver type structurally cannot collide, so plain names (`ToListAsync`, `ToItemsResultAsync`, ...) are safe there; see [`CoreEx.Cosmos/AGENTS.md`](./src/CoreEx.Cosmos/AGENTS.md#do-not) for the worked example. Only fall back to prefixing with the provider name (`ToCosmosListAsync`, `ToCosmosItemsResultAsync`, ...) if a package genuinely must expose `IQueryable<T>` extensions directly instead of owning a wrapper type.
 
 ---
 

CoreEx.Core.Test.Sequential.slnf

@@ -4,6 +4,7 @@
     "projects": [
       "tests/CoreEx.Azure.Messaging.ServiceBus.Test.Unit/CoreEx.Azure.Messaging.ServiceBus.Test.Unit.csproj",
       "tests/CoreEx.Caching.Redis.Test.Unit/CoreEx.Caching.Redis.Test.Unit.csproj",
+      "tests/CoreEx.Cosmos.Test.Unit/CoreEx.Cosmos.Test.Unit.csproj",
       "tests/CoreEx.Database.SqlServer.Test.Unit/CoreEx.Database.SqlServer.Test.Unit.csproj",
       "tests/CoreEx.Database.Postgres.Test.Unit/CoreEx.Database.Postgres.Test.Unit.csproj"
     ]

CoreEx.Core.slnf

@@ -7,6 +7,7 @@
       "src/CoreEx.AspNetCore.NSwag/CoreEx.AspNetCore.NSwag.csproj",
       "src/CoreEx.Azure.Messaging.ServiceBus/CoreEx.Azure.Messaging.ServiceBus.csproj",
       "src/CoreEx.Caching.FusionCache/CoreEx.Caching.FusionCache.csproj",
+      "src/CoreEx.Cosmos/CoreEx.Cosmos.csproj",
       "src/CoreEx.Data/CoreEx.Data.csproj",
       "src/CoreEx.Data.GraphQL/CoreEx.Data.GraphQL.csproj",
       "src/CoreEx.Database/CoreEx.Database.csproj",
@@ -23,6 +24,7 @@
       "tests/CoreEx.AspNetCore.Test.Unit/CoreEx.AspNetCore.Test.Unit.csproj",
       "tests/CoreEx.Azure.Messaging.ServiceBus.Test.Unit/CoreEx.Azure.Messaging.ServiceBus.Test.Unit.csproj",
       "tests/CoreEx.Caching.Redis.Test.Unit/CoreEx.Caching.Redis.Test.Unit.csproj",
+      "tests/CoreEx.Cosmos.Test.Unit/CoreEx.Cosmos.Test.Unit.csproj",
       "tests/CoreEx.Data.Test.Unit/CoreEx.Data.Test.Unit.csproj",
       "tests/CoreEx.Data.GraphQL.Test.Unit/CoreEx.Data.GraphQL.Test.Unit.csproj",
       "tests/CoreEx.Database.Postgres.Test.Unit/CoreEx.Database.Postgres.Test.Unit.csproj",

CoreEx.Samples.Build.slnf

@@ -3,6 +3,11 @@
     "path": "CoreEx.slnx",
     "projects": [
       "samples/aspire/Contoso.Aspire/Contoso.Aspire.csproj",
+      "samples/src/Contoso.Customers.Api/Contoso.Customers.Api.csproj",
+      "samples/src/Contoso.Customers.Application/Contoso.Customers.Application.csproj",
+      "samples/src/Contoso.Customers.CodeGen/Contoso.Customers.CodeGen.csproj",
+      "samples/src/Contoso.Customers.Contracts/Contoso.Customers.Contracts.csproj",
+      "samples/src/Contoso.Customers.Infrastructure/Contoso.Customers.Infrastructure.csproj",
       "samples/src/Contoso.Order.Workflow.Client/Contoso.Order.Workflow.Client.csproj",
       "samples/src/Contoso.Order.Workflow.Worker/Contoso.Order.Workflow.Worker.csproj",
       "samples/src/Contoso.Order.Workflow.Workflow/Contoso.Order.Workflow.Workflow.csproj",
@@ -28,6 +33,9 @@
       "samples/src/Contoso.Shopping.Infrastructure/Contoso.Shopping.Infrastructure.csproj",
       "samples/src/Contoso.Shopping.Relay/Contoso.Shopping.Relay.csproj",
       "samples/src/Contoso.Shopping.Subscribe/Contoso.Shopping.Subscribe.csproj",
+      "samples/tests/Contoso.Customers.Test.Api/Contoso.Customers.Test.Api.csproj",
+      "samples/tests/Contoso.Customers.Test.Common/Contoso.Customers.Test.Common.csproj",
+      "samples/tests/Contoso.Customers.Test.Unit/Contoso.Customers.Test.Unit.csproj",
       "samples/tests/Contoso.E2E.Runner/Contoso.E2E.Runner.csproj",
       "samples/tests/Contoso.Orders.Test.Api/Contoso.Orders.Test.Api.csproj",
       "samples/tests/Contoso.Orders.Test.Common/Contoso.Orders.Test.Common.csproj",

CoreEx.Samples.Test.slnf

@@ -2,6 +2,8 @@
   "solution": {
     "path": "CoreEx.slnx",
     "projects": [
+      "samples/tests/Contoso.Customers.Test.Api/Contoso.Customers.Test.Api.csproj",
+      "samples/tests/Contoso.Customers.Test.Unit/Contoso.Customers.Test.Unit.csproj",
       "samples/tests/Contoso.Orders.Test.Api/Contoso.Orders.Test.Api.csproj",
       "samples/tests/Contoso.Orders.Test.Unit/Contoso.Orders.Test.Unit.csproj",
       "samples/tests/Contoso.Products.Test.Api/Contoso.Products.Test.Api.csproj",