Add post permalinks

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

@@ -462,6 +462,9 @@ func TestQuestionPageRendersNestedPostControls(t *testing.T) {
 		`data-submit-button`,
 		`action="/posts/` + root.ID + `/edit"`,
 		`action="/posts/` + homeownerReply.ID + `/edit"`,
+		`href="/questions/` + root.ID + `#post-` + root.ID + `"`,
+		`href="/questions/` + root.ID + `#post-` + homeownerReply.ID + `"`,
+		`href="/questions/` + root.ID + `#post-` + adminReply.ID + `"`,
 		`>The model number is 123A.</textarea>`,
 		`removeAttribute('open')`,
 	} {
@@ -469,6 +472,9 @@ func TestQuestionPageRendersNestedPostControls(t *testing.T) {
 			t.Fatalf("question page missing %q: %s", want, body)
 		}
 	}
+	if got := strings.Count(body, ">Permalink</a>"); got != 3 {
+		t.Fatalf("question page rendered %d permalinks, want 3: %s", got, body)
+	}
 	if strings.Contains(body, `action="/posts/`+adminReply.ID+`/edit"`) {
 		t.Fatalf("homeowner can edit admin reply: %s", body)
 	}

static/app.css

@@ -749,6 +749,11 @@ input:focus, textarea:focus, .btn:focus-visible, .chip:focus-visible, .vote-btn:
 
 .post-form-actions .btn { flex: 1 1 10rem; }
 
+.post-permalink {
+  display: inline-flex;
+  align-items: center;
+}
+
 .post-hide {
   margin: 0;
 }

templates/partials/_post.html

@@ -33,6 +33,9 @@
       </form>
     </details>
   {{end}}
+  <a class="linkish post-permalink"
+    href="/questions/{{.Root.ID}}#post-{{.Post.ID}}"
+    aria-label="Permanent link to post by {{.Post.AuthorName}}">Permalink</a>
   {{if and (not .Post.ParentID) (isAdmin .User)}}
     <form class="post-hide" method="post" action="/questions/{{.Post.ID}}/hide">
       <input type="hidden" name="_csrf" value="{{.CSRF}}">