change client_secret fromt string to text

closes #81

Author: Boy132

generic-oidc-providers/database/migrations/001_create_generic_oidc_providers_table.php

@@ -17,7 +17,7 @@ public function up(): void
             $table->string('display_color', 6)->nullable();
             $table->string('base_url');
             $table->string('client_id');
-            $table->string('client_secret');
+            $table->text('client_secret');
             $table->boolean('verify_jwt')->default(false);
             $table->text('jwt_public_key')->nullable();
             $table->timestamps();