Create Background Processing Infrastructure: Create perflab_background_process_next_batch function

[jjgrainger]

Create a new perflab_background_process_next_batch function to handle subsequent requests to process additional job batches.

This function is created in the module file called modules/images/regenerate-existing-images/background-process.php

Acceptance Criteria

• Function accepts the following parameters
  • $job_id - A integer that is the ID for a job to run the next batch for.
• The function will create a new requests key to pass in the request.
  • Generate a random key with the wp_generate_password function
  • Save that key to the options table with the key background_process_key_{$job_id}
• The function will make a HTTP request to the admin-ajax.php endpoint with the wp_remote_post along with the following parameters
  • action: wp_ajax_background_process_next_batch
  • timeout: 0.1
  • data: array( 'job_id' => $job_id, 'key' => $key )
  • blocking: false
  • sslverify: apply_filters( 'https_local_ssl_verify', false )
• The function will return the following depending on success or failure
  • On failure the function returns the WP_Error from wp_remote_post
  • On success, the function returns true