Expanding ObservationIntentType to include outreach

[dr-rodriguez]

STScI has been ingesting observations encapsulating images created by the Office of Public Outreach into our CAOM database. We've needed to use intent_type=science for these, but ideally we would prefer an outreach intent for them. This PR expands the enumeration in both the python and xsd file to support this option.

[andamian]

Thanks for the PR @dr-rodriguez. It looks good to me providing that ObservationIntendType could be expanded which https://www.opencadc.org/caom2/#ObservationIntentType doesn't seem to agree. What's your take on this @pdowler ?

[pdowler]

ObservationIntentType is currently an enum so modifying it means a new minor version of CAOM. If we think this is really extensible we could consider changing it to a vocabulary so that new terms can be added without a version update. That's still a minor version update, but one last time for this field.

technical: iirc, enums are enforced in the xml schema

The best place for a model RFE is in https://github.com/opencadc/caom2 and we'd have to decide on this solution vs vocabulary (to future proof it a bit more)

[pdowler]

aside: it would be good to indicate somehow that the xsd files here are not the definitive ones, but copies for the purpose of bundling with the package

I plane to further decouple the xsd files in the java lib in the same way - they come from the model, not the impl.

[dr-rodriguez]

I'm not as familiar with that other repo, but I opened an issue there: opencadc/CAOM#5