Remove legacy question storage (#7)

Deletes obsolete question/answer/vote persistence and the compatibility answer endpoint. Existing databases drop the legacy tables through migration 009. Plumber replies now notify the root homeowner even when nested beneath another plumber reply. Post and reply forms prevent duplicate submissions and show progress while posting.

Reviewed-on: #7
Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/web/posts_test.go

@@ -334,6 +334,22 @@ func TestPostReplyNotifications(t *testing.T) {
 		t.Fatalf("homeowner reply notification = %+v", msg)
 	}
 
+	rec = postForm(handler, "/posts", url.Values{
+		"_csrf":     {adminCSRF},
+		"parent_id": {adminReply.ID},
+		"body":      {"One more plumber detail."},
+	}, adminCookies)
+	if rec.Code != http.StatusSeeOther {
+		t.Fatalf("nested admin reply status = %d: %s", rec.Code, rec.Body.String())
+	}
+	msgs = waitForMail(t, recording, 3)
+	if msg := msgs[2]; msg.ToEmail != homeowner.Email ||
+		msg.RootID != root.ID ||
+		msg.ReplyBody != "One more plumber detail." ||
+		msg.ReplyAuthorName != admin.Name {
+		t.Fatalf("nested admin reply notification = %+v", msg)
+	}
+
 	rec = postForm(handler, "/posts", url.Values{
 		"_csrf":     {homeownerCSRF},
 		"parent_id": {root.ID},
@@ -376,7 +392,7 @@ func TestPostReplyNotifications(t *testing.T) {
 		t.Fatalf("no-email reply status = %d: %s", rec.Code, rec.Body.String())
 	}
 	time.Sleep(50 * time.Millisecond)
-	if recording.Len() != 2 {
+	if recording.Len() != 3 {
 		t.Fatalf("self, edit, or no-email action sent a notification: %+v", recording.Snapshot())
 	}
 }
@@ -442,6 +458,8 @@ func TestQuestionPageRendersNestedPostControls(t *testing.T) {
 		"Shop response",
 		"Edited",
 		`action="/posts"`,
+		`data-submit-once`,
+		`data-submit-button`,
 		`action="/posts/` + root.ID + `/edit"`,
 		`action="/posts/` + homeownerReply.ID + `/edit"`,
 		`>The model number is 123A.</textarea>`,