Add language detection and default value settings to bulk document indexing in Admin API

[marevol]

We have implemented a feature in the Admin API that allows for bulk document indexing with language detection and default value settings. This update includes:

• Automatic language detection for documents
• Default values for fields such as content length, favorite count, click count, boost, role, last modified, and timestamp
• Proper handling of language field if set to 'auto'

This change aims to enhance the efficiency and accuracy of the document indexing process.