Use lazy loading when response type is OPeNDAP

[vinisalazar]

Hi,

this closes #250.

Summary of changes

• On method ERDDAP.to_xarray, check if response type is opendap. If it is, pass the URL to the xarray.open_dataset method instead of an nc dataset. This allows lazy loading of the dataset.
• Add corresponding tests (based on the 01a-griddap notebook).

Please feel free to request any changes.

Thank you,
Vini

[vinisalazar]

Not sure what went wrong with the Windows tests... Should we skip this for Windows and macOS like it's done with the iris tests? I'm also wondering why it worked on Py 3.10.

[ocefpaf]

The failures are happening b/c that ERDDAP server is too restrictive. I need to figure out a way to use VCR there, or change the server, or mock the test. For now, we can just re-start the test and get it working from a fresh GH VM (and new IP).

E   OSError: [Errno -78] NetCDF: Authorization failure: b'https://coastwatch.pfeg.noaa.gov/erddap/griddap/jplAquariusSSS3MonthV5'
src\netCDF4\_netCDF4.pyx:1925: OSError
---------------------------- Captured stderr call -----------------------------
syntax error, unexpected $end, expecting ';'
context: Error { code=403; message="Forbidden: Access Forbidden -- Your IP address is on this ERDDAP's request blacklist.Did you often submit more than one request at a time?Did you often submit identical requests in a short period of time?Did you submit a large number of invalid requests?If you are ready to avoid these problems, please email bob.simons@noaa.gov to request to be taken off of the blacklist.";}^