feat: add "copy link" button for sharing a grid view

src/wuttaweb/templates/grids/vue_template.mako

@@ -16,6 +16,13 @@
                             ref="gridFilters" />
 
               <div class="buttons">
+
+                <b-button @click="copyDirectLink()"
+                          title="Copy grid link to clipboard"
+                          :is-small="smallFilters">
+                  <b-icon pack="fas" icon="share-alt" />
+                </b-button>
+
                 <b-button type="is-primary"
                           native-type="submit"
                           icon-pack="fas"
@@ -209,6 +216,12 @@
         % endif
 
     </${b}-table>
+
+    ## dummy input field needed for sharing links on *insecure* sites
+    % if getattr(request, 'scheme', None) == 'http':
+        <b-input v-model="shareLink" ref="shareLink" v-show="shareLink"></b-input>
+    % endif
+
   </div>
 </script>
 
@@ -223,6 +236,11 @@
       ## nb. this tracks whether grid.fetchFirstData() happened
       fetchedFirstData: false,
 
+      ## dummy input value needed for sharing links on *insecure* sites
+      % if getattr(request, 'scheme', None) == 'http':
+          shareLink: null,
+      % endif
+
       ## filtering
       % if grid.filterable:
           filters: ${json.dumps(grid.get_vue_filters())|n},
@@ -268,6 +286,11 @@
       template: '#${grid.vue_tagname}-template',
       computed: {
 
+          directLink() {
+              const params = new URLSearchParams(this.getAllParams())
+              return `${request.path_url}?${'$'}{params}`
+          },
+
           % if grid.filterable:
 
               addFilterChoices() {
@@ -346,12 +369,50 @@
 
       methods: {
 
+          copyDirectLink() {
+
+              if (navigator.clipboard) {
+                  // this is the way forward, but requires HTTPS
+                  navigator.clipboard.writeText(this.directLink)
+
+              } else {
+                  // use deprecated 'copy' command, but this just
+                  // tells the browser to copy currently-selected
+                  // text..which means we first must "add" some text
+                  // to screen, and auto-select that, before copying
+                  // to clipboard
+                  this.shareLink = this.directLink
+                  this.$nextTick(() => {
+                      let input = this.$refs.shareLink.$el.firstChild
+                      input.select()
+                      document.execCommand('copy')
+                      // re-hide the dummy input
+                      this.shareLink = null
+                  })
+              }
+
+              this.$buefy.toast.open({
+                  message: "Link was copied to clipboard",
+                  type: 'is-info',
+                  duration: 2000, // 2 seconds
+              })
+          },
+
           renderNumber(value) {
               if (value != undefined) {
                   return value.toLocaleString('en')
               }
           },
 
+          getAllParams() {
+              return {
+                  ...this.getBasicParams(),
+                  % if grid.filterable:
+                      ...this.getFilterParams(),
+                  % endif
+              }
+          },
+
           getBasicParams() {
               const params = {
                   % if grid.paginated and grid.paginate_on_backend: