Support for spatial extent filtering in API v2

[Samweli]

Fixes #162

Enables support for spatial extent filtering in API v2.

screenshot with a sample spatial extent filtering

[ricardogsilva]

This seems to work sometimes, but not others. It could be a bug on the remote GeoNode, but please investigate.

Take a look at this brief video:

2021-05-17.12-13-15.mp4

As you can see, I'm providing a search spatial extent that is in Vanuatu. I can see on the GeoNode website that data exists for that region. However, when I perform a spatial search inside the plugin I don't get any results back. Could this be a bug on the remote GeoNode?

There are some additional things I'd like to have done in this PR too:

• Please rename the label for this widget to Spatial Extent instead of Extent. We already have Temporal Extent in there, so it makes sense to call this spatial extent

• Sometimes QGIS' datasource manager window becomes too big and its border disappears off screen, as shown in this video:

  2021-05-17.12-25-44.mp4

  Please comment on whether this is something that you are able to fix in this PR of if it requires deeper research (in which case I will open a separate issue for it)

• Now that I am using it I notice that this particular widget is very clunky to reset, as there is no button to set the extent to be global. Please provide a convenient way to come back to a global extent. I guess you can either:

  • hack the widget in order to put an additional button in there to allow the user to choose a global extent,
  • make the whole group box checkable and allow the user to disable this particular search param by unchecking it.

  I'm fine with either of these approaches, please pick one of them and implement it

[Samweli]

• Please comment on whether this is something that you are able to fix in this PR of if it requires deeper research (in which case I will open a separate issue for it)

I have not been able to reproduce the issue, maybe it happens only on certain screen settings!?

[Samweli]

However, when I perform a spatial search inside the plugin I don't get any results back. Could this be a bug on the remote GeoNode?

This looks like it is from the GeoNode instance as the extent parameter values are correctly set and sent.