Archive snapshots of websites locally (#672)

* Add basic HTML snapshots

* Implement asset list

* Add snapshot creation tests

* Add deletion tests

* Show file size

* Remove snapshots

* Create new snapshots

* Switch to single-file

* CSS tweak

* Remove auto refresh

* Show delete link when there is no file yet

* Add current date to display name

* Add flag for snapshot support

* Add option for disabling automatic snapshots

* Make snapshots sharable

* Document image variants

* Update README.md

* Add migrations

* Fix tests

siteroot/settings/base.py

@@ -269,3 +269,20 @@ LD_ENABLE_REFRESH_FAVICONS = os.getenv("LD_ENABLE_REFRESH_FAVICONS", True) in (
     "True",
     "1",
 )
+
+# Asset / snapshot settings
+LD_ASSET_FOLDER = os.path.join(BASE_DIR, "data", "assets")
+
+LD_ENABLE_SNAPSHOTS = os.getenv("LD_ENABLE_SNAPSHOTS", False) in (
+    True,
+    "True",
+    "1",
+)
+LD_SINGLEFILE_PATH = os.getenv("LD_SINGLEFILE_PATH", "single-file")
+LD_SINGLEFILE_OPTIONS = os.getenv("LD_SINGLEFILE_OPTIONS", "")
+
+# Monolith isn't used at the moment, as the local snapshot implementation
+# switched to single-file after the prototype. Keeping this around in case
+# it turns out to be useful in the future.
+LD_MONOLITH_PATH = os.getenv("LD_MONOLITH_PATH", "monolith")
+LD_MONOLITH_OPTIONS = os.getenv("LD_MONOLITH_OPTIONS", "-a -v -s")