wip: Filter by custom fields in graph ql

[christophbeberweil]

Works on : #7598

I worked on issue #7598 and made progress. Unfortunaltely, I hit some roadblocks and none of the maintainers were available to answer my questions. I open this merge request with my partial solution so that it might be of use for the project in the future.

I utilized autotype_decorator, which is used to communicate the filterset to graphql, in order to add CustomField entries with the same logic applied as in netbox.filtersets.NetBoxModelFilterSet. The code calls create_attribute_and_function for each custom field of the current model. This successfully adds a new filter to GraphQL, which is recognized in the backend. Unfortunately, there are still some problems:

• The generated Filter itereates over the filter argument, so a filter by "Foo" filters by "F" OR "o" OR "o", which is not the desired functionality.
• Additionally, filters on non-iterable datatypes such as int do not work.
• After adding a new CustomField, the server needs to be restarted in order for GraphQL to be aware of the new field. Since GraphQL is a schema-based tool, it is not clear if the restart requirement can be avoided.
• The lints in the GraphIQL-Frontend do not recognize the new CustomField filter. Nevertheless, applying the filter will lead to a change in the output, so it is recognized by the server. For instance, after creating a custom field a_string on Device, the following graphql statement can be used to filter the devices, but GraphIQL does not know of cf_a_string:

  {
  device_list(filters: {cf_a_string: "a"}) {
  id
  name
  custom_fields
  local_context_data
  device_type {
  id
  display
  slug
  }
  }
  }