Add docs for security models (#9)

- Change default security to CONFIGURE_ME
- Fix log on return URL handling
- Update INSTALLING security model descriptions

src/public/assets/style.css

@@ -70,6 +70,10 @@ article {
         }
     }
 }
+article.docs {
+    line-height: 1.4rem;
+}
+
 input[type=url],
 input[type=text],
 input[type=email],
@@ -103,3 +107,9 @@ button:hover,
     flex-flow: row nowrap;
     justify-content: space-evenly;
 }
+code {
+    font-size: .9rem;
+}
+p.back-link {
+    margin-top: -1rem;
+}