Migrated to obs4REF, ready for esgvoc integration

[dwest77a]

No description provided.

[dwest77a]

@ltroussellier could you take a look at this PR for adding an esgvoc manifest to obs4REF and see if this can be added to esgvoc now?

[dwest77a]

The guidance I have includes adding all the CV values here to the WCRP universe as well. I'm attempting to do this, but have noticed the following:

• Obs4REF nominal resolutions have no space in the value (i.e 5km) versus the value in the WCRP-universe that includes a dash (i.e 5-km). Should this be changed in Obs4REF to match the universe?
• Obs4REF folders (e.g activity_id, variable_id) do not match their universe counter parts (e.g activity, variable) in the naming convention. Is this acceptable for the schema or should this be changed to match the universe?
• Other Obs4REF folders have similar naming differences (grid_label -> grid, references -> reference)
• The values for source_type in Obs4REF do not appear to be similar to the equivalent in the universe - is this the correct set of values for source type or is this a different facet's values?