fix: Fix fields and filter fields mixup

Django Graphene / Django Filters have a slightly different interface
for declaring filter fields on DjangoObjectType and FilterSet.

terraso_backend/apps/graphql/schema/schema.graphql

@@ -30,7 +30,7 @@ type Query {
   ): GroupAssociationNode!
   groups(offset: Int, before: String, after: String, first: Int, last: Int, name: String, name_Icontains: String, name_Istartswith: String, slug: String, slug_Icontains: String, description_Icontains: String, memberships_Email: String, associatedLandscapes_IsDefaultLandscapeGroup: Boolean, associatedLandscapes_Isnull: Boolean, associatedLandscapes_IsPartnership: Boolean): GroupNodeConnection
   landscapes(offset: Int, before: String, after: String, first: Int, last: Int, name_Icontains: String, description_Icontains: String, slug: String, slug_Icontains: String, website_Icontains: String, location_Icontains: String): LandscapeNodeConnection
-  users(offset: Int, before: String, after: String, first: Int, last: Int, email: String, firstName: String, lastName: String, profileImage: String, memberships: ID, preferences: ID, user_InProject: String): UserNodeConnection
+  users(offset: Int, before: String, after: String, first: Int, last: Int, email: String, email_Icontains: String, firstName_Icontains: String, lastName_Icontains: String, user_InProject: String): UserNodeConnection
   landscapeGroups(offset: Int, before: String, after: String, first: Int, last: Int, landscape: ID, landscape_Slug_Icontains: String, group: ID, group_Slug_Icontains: String, isDefaultLandscapeGroup: Boolean, isPartnership: Boolean): LandscapeGroupNodeConnection
   memberships(offset: Int, before: String, after: String, first: Int, last: Int, group: ID, group_In: [ID], group_Slug_Icontains: String, group_Slug_In: [String], user: ID, user_In: [ID], userRole: CoreMembershipUserRoleChoices, user_Email_Icontains: String, user_Email_In: [String], membershipStatus: CoreMembershipMembershipStatusChoices): MembershipNodeConnection
   groupAssociations(offset: Int, before: String, after: String, first: Int, last: Int, parentGroup: ID, childGroup: ID, parentGroup_Slug_Icontains: String, childGroup_Slug_Icontains: String): GroupAssociationNodeConnection

terraso_backend/apps/graphql/schema/users.py

@@ -41,12 +41,11 @@ class UserFilter(FilterSet):
 
     class Meta:
         model = User
-        filter_fields = {
+        fields = {
             "email": ["exact", "icontains"],
             "first_name": ["icontains"],
             "last_name": ["icontains"],
         }
-        fields = ("email", "first_name", "last_name", "profile_image", "memberships", "preferences")
 
     def filter_user_in_project(self, queryset, name, value):
         return queryset.filter(collaboration_memberships__membership_list__project__id=value)