feat: Add authentication and personal user endpoint (#29)

* feat: Add authentication and personal user endpoint

This contribution adds a lot of scaffolding for the database fake
and testability of coderd.

A new endpoint "/user" is added to return the currently authenticated
user to the requester.

* Use TestMain to catch leak instead

* Add userpassword package

* Add WIP

* Add user auth

* Fix test

* Add comments

* Fix login response

* Fix order

* Fix generated code

* Update httpapi/httpapi.go

Co-authored-by: Bryan <bryan@coder.com>

Co-authored-by: Bryan <bryan@coder.com>

codersdk/users_test.go

@@ -0,0 +1,33 @@
+package codersdk_test
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"github.com/coder/coder/coderd"
+	"github.com/coder/coder/coderd/coderdtest"
+	"github.com/coder/coder/codersdk"
+	"github.com/stretchr/testify/require"
+)
+
+func TestUsers(t *testing.T) {
+	t.Run("MultipleInitial", func(t *testing.T) {
+		server := coderdtest.New(t)
+		_, err := server.Client.CreateInitialUser(context.Background(), coderd.CreateUserRequest{
+			Email:    "wowie@coder.com",
+			Username: "tester",
+			Password: "moo",
+		})
+		var cerr *codersdk.Error
+		require.ErrorAs(t, err, &cerr)
+		require.Equal(t, cerr.StatusCode(), http.StatusConflict)
+		require.Greater(t, len(cerr.Error()), 0)
+	})
+
+	t.Run("Get", func(t *testing.T) {
+		server := coderdtest.New(t)
+		_, err := server.Client.User(context.Background(), "")
+		require.NoError(t, err)
+	})
+}