add reference URL to proposal

[pdowler]

to refer to the details of the propsal (abstract, document, etc)
some telescopes provide the endpoint

[pdowler]

ESAC syncs propsal info for HST from MAST in a way that's loosely coupled with CAOM observations (same proposal_id in that other content)... should look at that.

[ijiraq]

Sometimes the references are adhoc (to a paper that describes a project) rather than to a telescope/observatory provided reference.

[pdowler]

@ijiraq Would a URI always be sufficient to reference a paper? iirc, anything in ADS has a DOI so that's available to any paper published in astronomy. A URI would be "resolvable" by a human (at least) and by software > 95% of the time with minimal effort.

[ijiraq]

Yes. a URI would be sufficient and likey a preferred solution.