Add many-to-many mapping for Identity Users/Roles relationship (#23973)

Checks that skip navigations can be layered over the existing model; see #23951.

test/EFCore.AspNet.Specification.Tests/AspNetIdentityCustomTypesDefaultTestBase.cs

@@ -63,6 +63,42 @@ await ExecuteWithStrategyInTransactionAsync(
                 });
         }
 
+        [ConditionalFact]
+        public async Task Can_lazy_load_User_navigations_many_to_many()
+        {
+            var userId = "";
+
+            await ExecuteWithStrategyInTransactionAsync(
+                async context =>
+                {
+                    var user = new CustomUserString { NormalizedUserName = "wendy" };
+                    await CreateUser(context, user);
+                    userId = user.Id;
+                },
+                async context =>
+                {
+                    var user = await context.Users.SingleAsync(u => u.Id == userId);
+
+                    Assert.Equal(2, user.Roles.Count);
+                });
+        }
+
+        [ConditionalFact]
+        public async Task Can_lazy_load_Role_navigations_many_to_many()
+        {
+            await ExecuteWithStrategyInTransactionAsync(
+                async context =>
+                {
+                    await CreateUser(context, new CustomUserString { NormalizedUserName = "wendy" });
+                },
+                async context =>
+                {
+                    var role = await context.Roles.OrderBy(e => e.NormalizedName).FirstAsync();
+
+                    Assert.Equal(1, role.Users.Count);
+                });
+        }
+
         [ConditionalFact]
         public async Task Can_lazy_load_UserRole_navigations()
         {
@@ -183,6 +219,10 @@ protected override List<EntityTypeMapping> ExpectedMappings
                         "Navigation: CustomRoleString.RoleClaims (ICollection<CustomRoleClaimString>) Collection ToDependent CustomRoleClaimString Inverse: Role PropertyAccessMode.Field",
                         "Navigation: CustomRoleString.UserRoles (ICollection<CustomUserRoleString>) Collection ToDependent CustomUserRoleString Inverse: Role PropertyAccessMode.Field",
                     },
+                    SkipNavigations =
+                    {
+                        "SkipNavigation: CustomRoleString.Users (ICollection<CustomUserString>) CollectionCustomUserString Inverse: Roles PropertyAccessMode.Field"
+                    }
                 },
                 new EntityTypeMapping()
                 {
@@ -248,7 +288,7 @@ protected override List<EntityTypeMapping> ExpectedMappings
                     {
                         "Navigation: CustomUserRoleString.Role (CustomRoleString) ToPrincipal CustomRoleString Inverse: UserRoles PropertyAccessMode.Field",
                         "Navigation: CustomUserRoleString.User (CustomUserString) ToPrincipal CustomUserString Inverse: UserRoles PropertyAccessMode.Field",
-                    },
+                    }
                 },
                 new EntityTypeMapping()
                 {
@@ -285,6 +325,10 @@ protected override List<EntityTypeMapping> ExpectedMappings
                         "Navigation: CustomUserString.Tokens (ICollection<CustomUserTokenString>) Collection ToDependent CustomUserTokenString Inverse: User PropertyAccessMode.Field",
                         "Navigation: CustomUserString.UserRoles (ICollection<CustomUserRoleString>) Collection ToDependent CustomUserRoleString Inverse: User PropertyAccessMode.Field",
                     },
+                    SkipNavigations =
+                    {
+                        "SkipNavigation: CustomUserString.Roles (ICollection<CustomRoleString>) CollectionCustomRoleString Inverse: Users PropertyAccessMode.Field"
+                    }
                 },
                 new EntityTypeMapping()
                 {
@@ -328,6 +372,12 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
             modelBuilder.Entity<CustomUserString>(
                 b =>
                 {
+                    b.HasMany(e => e.Roles)
+                        .WithMany(e => e.Users)
+                        .UsingEntity<CustomUserRoleString>(
+                            j => j.HasOne(e => e.Role).WithMany(e => e.UserRoles).HasForeignKey(e => e.RoleId),
+                            j => j.HasOne(e => e.User).WithMany(e => e.UserRoles).HasForeignKey(e => e.RoleId));
+
                     b.HasMany(e => e.Claims).WithOne(e => e.User).HasForeignKey(uc => uc.UserId).IsRequired();
                     b.HasMany(e => e.Logins).WithOne(e => e.User).HasForeignKey(ul => ul.UserId).IsRequired();
                     b.HasMany(e => e.Tokens).WithOne(e => e.User).HasForeignKey(ut => ut.UserId).IsRequired();
@@ -390,6 +440,8 @@ public CustomUserString()
 
         public string CustomTag { get; set; }
 
+        public virtual ICollection<CustomRoleString> Roles { get; set; }
+
         public virtual ICollection<CustomUserClaimString> Claims { get; set; }
         public virtual ICollection<CustomUserLoginString> Logins { get; set; }
         public virtual ICollection<CustomUserTokenString> Tokens { get; set; }
@@ -403,6 +455,8 @@ public CustomRoleString()
             Id = Guid.NewGuid().ToString();
         }
 
+        public virtual ICollection<CustomUserString> Users { get; set; }
+
         public virtual ICollection<CustomUserRoleString> UserRoles { get; set; }
         public virtual ICollection<CustomRoleClaimString> RoleClaims { get; set; }
     }