LEGLINK-951: Return 404 from DMRP endpoints when the module is disabled (#1817)

The Tenant build emits [assembly: ApplicationPart(DMRP)] for the DMRP
project reference, so AddControllers() discovered the module's
controllers even when DMRP:Enabled was false or missing. With no DMRP
services registered, activating those controllers threw
InvalidOperationException and every DMRP request returned 500.

AddDmrpModule now strips the module's application part when the flag is
off, so the routes are never mapped and requests fall through to 404.

Claude-Session: https://claude.ai/code/session_01LVVXQjfgjXC4WwHtciJYEJ

Author: arianamihailescu

DotNet/DMRP/DependencyInjection/DmrpModuleExtensions.cs

@@ -35,6 +35,16 @@ public static bool AddDmrpModule<TDbContext>(this WebApplicationBuilder builder,
 
             if (section.Get<DmrpSettings>()?.Enabled != true)
             {
+                // The host's build emits [assembly: ApplicationPart("DMRP")] for the project reference,
+                // so MVC discovers this module's controllers before AddDmrpModule runs. Left in place
+                // without their services, those controllers turn every DMRP request into a 500; strip
+                // the part so a disabled module has no routes at all.
+                var moduleAssemblyName = typeof(DmrpModuleExtensions).Assembly.GetName().Name;
+                foreach (var part in mvcBuilder.PartManager.ApplicationParts.Where(p => p.Name == moduleAssemblyName).ToList())
+                {
+                    mvcBuilder.PartManager.ApplicationParts.Remove(part);
+                }
+
                 return false;
             }
 

DotNet/ServiceTests/UnitTests/DMRP/DmrpModuleExtensionsTests.cs

@@ -145,5 +145,30 @@ public void AddDmrpModule_registers_nothing_when_disabled_or_unset(bool? enabled
             var dmrpAssembly = typeof(MeasureMapping).Assembly;
             Assert.DoesNotContain(mvcBuilder.PartManager.ApplicationParts, p => p.Name == dmrpAssembly.GetName().Name);
         }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(null)]
+        public void AddDmrpModule_removes_the_hosts_auto_discovered_part_when_disabled(bool? enabled)
+        {
+            var builder = CreateBuilder(enabled);
+            var mvcBuilder = builder.Services.AddControllers();
+
+            // The Tenant build emits [assembly: ApplicationPart("DMRP")] for the project reference, so
+            // in the real host the module's assembly is an application part before AddDmrpModule runs.
+            // Recreate that here: the module must strip the part, or its controllers would be routable
+            // without their services and every DMRP request would 500 instead of 404.
+            var dmrpAssembly = typeof(MeasureMapping).Assembly;
+            mvcBuilder.AddApplicationPart(dmrpAssembly);
+
+            var registered = builder.AddDmrpModule<TenantDbContext>(mvcBuilder);
+
+            Assert.False(registered);
+            Assert.DoesNotContain(mvcBuilder.PartManager.ApplicationParts, p => p.Name == dmrpAssembly.GetName().Name);
+
+            var controllers = new ControllerFeature();
+            mvcBuilder.PartManager.PopulateFeature(controllers);
+            Assert.DoesNotContain(controllers.Controllers, c => c.Assembly == dmrpAssembly);
+        }
     }
 }