Account Issue Model and Resolution Flow + Troubleshooting guides (#1090)

* Rough draft of issue system

* Simplify design

* Remove stale files from merge conflicts

* STI for issues

* Cleanup

* Improve Synth api key flow

* Stub api key for test

app/views/issue/unknowns/show.html.erb

@@ -0,0 +1,23 @@
+<%= content_for :title, @issue.title %>
+
+<%= content_for :description do %>
+  <p>An unknown issue has occurred.</p>
+
+  <pre><code><%= JSON.pretty_generate(@issue.data || "No data provided for this issue") %></code></pre>
+<% end %>
+
+<%= content_for :action do %>
+  <p>There is no fix for this issue yet.</p>
+
+  <p>Maybe is in active development and we value your feedback. There are a couple ways you can report this issue to
+    help us make Maybe better:</p>
+
+  <ul>
+    <li>Post in our <%= link_to "Discord server", "https://link.maybe.co/discord", target: "_blank" %></li>
+    <li>Open an issue on
+      our <%= link_to "Github repository", "https://github.com/maybe-finance/maybe/issues", target: "_blank" %></li>
+  </ul>
+
+  <p>If there is data shown in the code block above that you think might be helpful, please include it in your
+    report.</p>
+<% end %>