Add DataAdministrator role and optional contributor fields to support EMBER data management use cases

[guittari]

The Contributor model and RoleType enum in dandischema/models.py already cover most contributor types like Author, DataCurator, and DataCollector. For EMBER-DANDI, there are also contributors who help with data ingestion, embargo coordination, and metadata validation work that doesn’t always fit cleanly into the existing roles.

To better reflect these contributions, I’m proposing a few updates to the contributor roles and related metadata fields, based on notes and comments in the EMBERSet Draft Metadata Google Sheet (https://docs.google.com/spreadsheets/d/1eQTHz6WSTsT84_FXOs2g53ySDEmSy8LtvFN_bic8xB8/edit?gid=0#gid=0) in the “contributor” (now “role”) row.

[guittari]

@yarikoptic, I don’t currently have write access to create a branch, but I believe we should add something along the lines of the following under RoleType:

 #: Data Administrator
 DataAdministrator = "dcite:DataAdministrator"

[yarikoptic]

@guittari -- no special privileges needed - just create personal fork and submit PR from it.