Add subproject2subproject foreign-key constraints (#2521)

This continues our ongoing effort described in
#2093 to add foreign-key
constraints wherever possible for better data integrity.

database/migrations/2024_10_29_154630_subproject2subproject_foreign_keys.php

@@ -0,0 +1,42 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration {
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        echo "Adding subprojectid foreign key to subproject2subproject table...";
+        $num_deleted = DB::delete('DELETE FROM subproject2subproject WHERE subprojectid NOT IN (SELECT id FROM subproject)');
+        echo $num_deleted . ' invalid rows deleted' . PHP_EOL;
+
+        echo "Adding dependsonid foreign key to subproject2subproject table...";
+        $num_deleted = DB::delete('DELETE FROM subproject2subproject WHERE dependsonid NOT IN (SELECT id FROM subproject)');
+        echo $num_deleted . ' invalid rows deleted' . PHP_EOL;
+
+        Schema::table('subproject2subproject', function (Blueprint $table) {
+            $table->bigInteger('subprojectid')->change();
+            $table->bigInteger('dependsonid')->change();
+            $table->foreign('subprojectid')->references('id')->on('subproject')->cascadeOnDelete();
+            $table->foreign('dependsonid')->references('id')->on('subproject')->cascadeOnDelete();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('subproject2subproject', function (Blueprint $table) {
+            $table->integer('subprojectid')->change();
+            $table->integer('dependsonid')->change();
+            $table->dropForeign(['subprojectid']);
+            $table->dropForeign(['dependsonid']);
+        });
+    }
+};