Dashboards: Edit Chart Panel: Add proper chart key validation

Summary:
Add proper validation by actually querying for existing chart keys.
This replaces my quick and dirty code from D26378.

Closes T16281

Test Plan:
* Go to http://phorge.localhost/dashboard/panel/edit/?panelType=chart
* Enter rubbish into the "Chart" field or leave it empty and try to create that panel, get an error instead of creating a panel
* Enter a random 12 character chart key into the field, now get an error
* Enter an existing 12 character chart key into the field taken from `SELECT chartKey FROM phabricator_fact.fact_chart;`, succeed

Reviewers: O1 Blessed Committers, mainframe98

Reviewed By: O1 Blessed Committers, mainframe98

Subscribers: mainframe98, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T16281

Differential Revision: https://we.phorge.it/D26396

src/applications/dashboard/xaction/panel/PhabricatorDashboardChartPanelChartTransaction.php

···
 
     foreach ($xactions as $xaction) {
       $new = $xaction->getNewValue();
-      // per PhabricatorFactChart::newChartKey()
-      if (strlen($new) !== 12) {
+      if (!$this->loadChart($new)) {
         $errors[] = $this->newInvalidError(
-          pht('Chart must be specified by its %d character long key.', 12),
+          pht('Chart with this key does not exist. A chart must be '.
+          'specified by its %d character long key.',
+          12),
           $xaction);
         continue;
       }
     }
     return $errors;
+  }
+
+  private function loadChart($chart_key) {
+    // PhabricatorFactChartQuery does not exist so use queryfx_one()
+    $chart = new PhabricatorFactChart();
+    $conn_r = $chart->establishConnection('r');
+    $chart = queryfx_one(
+      $conn_r,
+      'SELECT
+        id
+        FROM %R
+        WHERE chartKey = %s',
+        $chart,
+        $chart_key);
+
+    return $chart;
   }
 
 }

src/infrastructure/storage/lisk/PhabricatorLiskDAO.php

···
 
 
   /**
+   * Get the database table name
+   * @return string Name of the database table
    * @task config
    */
   public function getTableName() {
···
   }
 
   /**
+   * Get the database name
+   * @return string Name of the database
    * @task config
    */
   abstract public function getApplicationName();