Once the appropriate changes have been made to the API and handle, DocumentSourceExtensionOptimizable should override getDependencies(). 

The pseudocode for DocumentSourceExtensionOptimizable::getDependencies() is as follows:

1. Call logicalStageHandle->getProperties()
2. Parse out requiredMetadataFields, providedMetadataFields, and preservesUpstreamMetadata
3. For each field in requiredMetadataFields:
   1. Check if the metadata field is known to the server
      1. If so, call deps->setNeedsMetadata(), adding the field
      2. If not, uassert
4. If preservesUpstreamMetadata is false, clear metadataAvailable.
5. For each field in providedMetadataFields:
   1. Check if the metadata field is known to the server
      1. If so, call deps->setMetadataAvailable(), adding the field
      2. If not, uassert

This ticket should implement this logic in `DocumentSourceExtensionOptimizable` and update the corresponding unit test. This ticket should not create a full e2e test for an extension.