feat: working on detail views.

Sources/App/DB/UserDB.swift

@@ -15,6 +15,7 @@ struct UserDB: Sendable {
   var create: @Sendable (User.Create) async throws -> User.DTO
   var delete: @Sendable (User.IDValue) async throws -> Void
   var fetchAll: @Sendable () async throws -> [User.DTO]
+  var get: @Sendable (User.IDValue) async throws -> User.DTO?
   var login: @Sendable (User) async throws -> UserToken
 }
 
@@ -46,6 +47,9 @@ extension UserDB: TestDependencyKey {
       fetchAll: {
         try await User.query(on: db).all().map { $0.toDTO() }
       },
+      get: { id in
+        try await User.find(id, on: db).map { $0.toDTO() }
+      },
       login: { user in
         let token = try user.generateToken()
         try await token.save(on: db)