Support updating of resource extra fields w/o including a path parameter

Description

This PR makes the path parameter to resource_update optional in order to support updating of resource extra fields.

While resource_patch ckan api allows for modifying the value of a given resource extra, it does not allow for deleting an extra that is no longer needed. (note that extras are not supported in the ckanr::resource_patch)

The current behavior only supports resource_update when a the file/url is being uploaded which may require an unnecessary download and reupload of a file just to remove a metadata field.

Todos

[X] make path an optional parameter
[x] add tests
[x] update documentation

Related Issue

Example

# update an existing resource with an extra
id <- resource_update(id$id, extras = list(foo='bar'))

# purge all extras
resource_update(id)

ropensci / ckanr