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

db/migrate/20240815125404_create_issues.rb

@@ -0,0 +1,14 @@
+class CreateIssues < ActiveRecord::Migration[7.2]
+  def change
+    create_table :issues, id: :uuid do |t|
+      t.references :issuable, type: :uuid, polymorphic: true
+      t.string :type
+      t.integer :severity
+      t.datetime :last_observed_at
+      t.datetime :resolved_at
+      t.jsonb :data
+
+      t.timestamps
+    end
+  end
+end