feat: URL preview support

from upstream MR https://gitlab.com/famedly/conduit/-/merge_requests/347
with the following changes (so far):
- remove hardcoded list of allowed hosts (strongly disagree with this,
even if it is desired, it should not be harcoded)
- add more allow config options for granularity via URL contains,
host contains, and domain is (explicit match) for security
- warn if a user is allowing all URLs to be previewed for security reasons
- replace an expect with proper error handling
- bump webpage to 2.0
- improved code style a tad

Co-authored-by: rooot <hey@rooot.gay>
Signed-off-by: rooot <hey@rooot.gay>
Signed-off-by: strawberry <strawberry@puppygock.gay>

src/service/media/data.rs

@@ -17,4 +17,15 @@ pub trait Data: Send + Sync {
         width: u32,
         height: u32,
     ) -> Result<(Option<String>, Option<String>, Vec<u8>)>;
+
+    fn remove_url_preview(&self, url: &str) -> Result<()>;
+
+    fn set_url_preview(
+        &self,
+        url: &str,
+        data: &super::UrlPreviewData,
+        timestamp: std::time::Duration,
+    ) -> Result<()>;
+
+    fn get_url_preview(&self, url: &str) -> Option<super::UrlPreviewData>;
 }