When adding or updating elements via Rest Api, for picker fields it is required to provide Id and name. Quite often the name is known, but not the id.
As picker fields are usually based on datasources, it would by great, when the api would be extended with methods to query datasources.
There should be at least two methods:
1) getting a list of all available datasources (overall / by application)
2) query a datasource with a filter. To make it easier, the filter should be passed in as query string