Add migration to set external ID's

This also produces an error if entities would get an external ID that is already in use somewhere else.

webapp/migrations/Version20240604202419.php

@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20240604202419 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Set external ID\'s for entities that don\'t have them';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $djPrefixed = [
+            'contest' => 'cid',
+            'language' => 'langid',
+            'problem' => 'probid',
+            'team' => 'teamid',
+            'team_affiliation' => 'affilid',
+            'team_category' => 'categoryid',
+        ];
+        $notPrefixed = [
+            'clarification' => 'clarid',
+            'submission' => 'submitid',
+            'user' => 'username',
+        ];
+
+        foreach ($djPrefixed as $table => $column) {
+            $this->setExternalIds($table, $column, 'dj-');
+        }
+
+        foreach ($notPrefixed as $table => $column) {
+            $this->setExternalIds($table, $column);
+        }
+    }
+
+    protected function setExternalIds(string $table, string $column, string $prefix = '')
+    {
+        $entries = $this->connection->fetchAllAssociative("SELECT $column FROM $table WHERE externalid IS NULL");
+        foreach ($entries as $entry) {
+            $newExternalId = $prefix . $entry[$column];
+            // Check if any entity already has this external ID
+            $existingEntity = $this->connection->fetchAssociative("SELECT externalid FROM $table WHERE externalid = :externalid", ['externalid' => $newExternalId]);
+            $humanReadableTable = ucfirst(str_replace('_', ' ', $table));
+            $this->abortIf((bool)$existingEntity, "$humanReadableTable entity with external ID $newExternalId already exists, manually set a different external ID");
+            $this->addSql("UPDATE $table SET externalid = :externalid WHERE $column = :$column", [
+                'externalid' => $newExternalId,
+                $column => $entry[$column],
+            ]);
+        }
+    }
+
+    public function down(Schema $schema): void
+    {
+        // No down migration needed
+    }
+
+    public function isTransactional(): bool
+    {
+        return false;
+    }
+}