Currently the creation of a target source is done by specifying its name (must be a valid Sesame identifier).

We need to make it a bit better in order to allow the estimation of target which might not have a name (yet) or which name is not valid.

The obvious solution is to add a name and coordinates option to the configuration so that the user can give whatever name to any target in the sky.
A query option should disable the use of custom coordinates and interpret the name accordingly.