`events_mgmt`: CreateOrUpdate Multiple EventMetadata objects for a Provider

### Expected Behaviour
Need the ability to do the following:
1. CreateOrUpdate Metadata for a provider
2. Add multiple eventMetadata objects while updating the metadata on a provider rather than one at a time.

### Actual Behaviour
No way to CreateOrUpdate EventMetadata on a provider
No way to add multiple EventMetadata objects to a provider

Start by locating the events_mgmt entry points and the existing EventMetadata and provider operations. Compare the current create/update behavior with the requested provider-level workflow; done means a provider's metadata can be created or updated and multiple EventMetadata objects can be added in one update.

Written by the indexing model from the issue text.