enhance Q1+ metadata

[juansensio]

For Q0 we ask some mandatory metadata but for Q1+ we rely entirely on STAC (so the metadata that we have for Q0 is not mantained).

Should we require a README.md file for all datasets? Or should we enforce metadata fields in the STAC catalog (can do this for Q2 with our own extension, but not for Q1, so maybe the best option is to ask for README.md always, this also simplifies upgrading from Q0 to Q1 and to Q2). Any thoughts @Patrick1G ?

[earthpulse]

improve Q1+ overall, using #122 as use case