Slightly improve the media experience (#452)

* Slightly improve the media experience

- Use a grid to display the list of media
- Add icons for non-image media preview
- Paginate the gallery
- Add links to the gallery in the editor and in the profile settings to make it more discoverable when you need it

Fixes #432

* Allow video and audio tags in SafeString

Otherwise we can't display their preview, nor show them in articles

Also show controls by default for these two elements

* Show fallback images for audio and unknown files, to make them more visible

* Add a new constructor to SafeString when the input is trusted and doesn't need to be escaped.

And use it to generate media previews.

* Make it possible to insert video/audio in articles

plume-models/src/safe_string.rs

@@ -19,12 +19,20 @@ lazy_static! {
     static ref CLEAN: Builder<'static> = {
         let mut b = Builder::new();
         b.add_generic_attributes(iter::once("id"))
-            .add_tags(iter::once("iframe"))
+            .add_tags(&[ "iframe", "video", "audio" ])
             .id_prefix(Some("postcontent-"))
             .url_relative(UrlRelative::Custom(Box::new(url_add_prefix)))
             .add_tag_attributes(
                 "iframe",
-                ["width", "height", "src", "frameborder"].iter().map(|&v| v),
+                [ "width", "height", "src", "frameborder" ].iter().map(|&v| v),
+            )
+            .add_tag_attributes(
+                "video",
+                [ "src", "title", "controls" ].iter(),
+            )
+            .add_tag_attributes(
+                "audio",
+                [ "src", "title", "controls" ].iter(),
             );
         b
     };
@@ -53,6 +61,18 @@ impl SafeString {
             value: CLEAN.clean(&value).to_string(),
         }
     }
+
+    /// Creates a new `SafeString`, but without escaping the given value.
+    ///
+    /// Only use when you are sure you can trust the input (when the HTML
+    /// is entirely generated by Plume, not depending on user-inputed data).
+    /// Prefer `SafeString::new` as much as possible.
+    pub fn trusted(value: impl AsRef<str>) -> Self {
+        SafeString {
+            value: value.as_ref().to_string()
+        }
+    }
+
     pub fn set(&mut self, value: &str) {
         self.value = CLEAN.clean(value).to_string();
     }