enhance available metadata

[graybeal]

Is your feature request related to a problem? If so please describe.
FAIR data requires that metadata be reasonably complete about the source processes and entities that produced the data, as well as other contextual information that may be essential to interpreting the data. Researchers need to be able to point to the source of the data and to verify the data coming from that source.

Describe the solution you'd like
A clear and concise description of what you want to happen.
Rich metadata about each variable's source should be captured by the Data Commons and made accessible via the wizard. Even if metadata changes from one value to the next, this should be reflected as well. Metadata should be provided as well-defined JSON-LD. Metadata sources should be identified with IRIs wherever possible, and controlled terms should be used whenever possible to describe the values.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.
If the data is to be used for research conclusions, providing only simple metadata is insufficient for publication. It can be acceptable for exploration, however.

Additional context
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Dataset-level metadata should be consistent with DataCite expectations, and is sufficient if it describes all the variables within that dataset and the dataset is consonant with the Statistical Variable.