Improve logic for Add Filter grid button/autocomplete

this should work for oruga as well as buefy

tailbone/templates/grids/complete.mako

@@ -294,6 +294,7 @@
       computed: {
 
           addFilterChoices() {
+              // nb. this returns all choices available for "Add Filter" operation
 
               // collect all filters, which are *not* already shown
               let choices = []
@@ -354,6 +355,13 @@
 
       methods: {
 
+          formatAddFilterItem(filtr) {
+              if (!filtr.key) {
+                  filtr = this.filters[filtr]
+              }
+              return filtr.label || filtr.key
+          },
+
           % if grid.click_handlers:
               cellClick(row, column, rowIndex, columnIndex) {
                   % for key in grid.click_handlers:

tailbone/templates/grids/filters.mako

@@ -32,7 +32,7 @@
                     v-model="addFilterTerm"
                     placeholder="Add Filter"
                     field="key"
-                    :custom-formatter="filtr => filtr.label"
+                    :custom-formatter="formatAddFilterItem"
                     open-on-focus
                     keep-first
                     icon-pack="fas"