remove pk for mysql db

Signed-off-by: lpete@vmware.com <lpete@vmware.com>

plugins/app-backend/migrations/20211229105307_init.js

@@ -20,15 +20,21 @@
  * @param {import('knex').Knex} knex
  */
 exports.up = async function up(knex) {
+  const isMySQL = knex.client.config.client.includes('mysql');
   return knex.schema.createTable('static_assets_cache', table => {
     table.comment(
       'A cache of static assets that where previously deployed and may still be lazy-loaded by clients',
     );
-    table
-      .text('path', 'text')
-      .unique()
-      .notNullable()
-      .comment('The path of the file');
+    if (!isMySQL) {
+      table
+        .text('path')
+        .primary()
+        .notNullable()
+        .comment('The path of the file');
+    } else {
+      // cannot have a unique key in mysql with a text column greater than 733 bytes
+      table.text('path').notNullable().comment('The path of the file');
+    }
     table
       .dateTime('last_modified_at')
       .defaultTo(knex.fn.now())