Instead of using an `import_map.json` file to define the versions for
dependencies, they are now defined directly within the import. Since the
`import_map.json` file should not be used anymore and instead a
`deno.json` file per function should be used, we decided to define them
directly with the code. The overhead compared to a `deno.json` file per
function shouldn't be that large and it makes using functions in a
self-hosted setup easier.
We have to add the "charset" parameter to the "Content-Type" header when
we return json from one of the Supabase functions, so that special
characters are properly decoded in Flutter.
Improve the media handling within the app. We do not save the media
files for items to the Supabase storage anymore. The source icons are
now only saved in the Supabase storage, the usage of an url as source
icon is not possible anymore.
The media files for items are directly retrieved from the corresponding
url or for the web version from the "image-proxy-v1" Supabase function.
If the image is retireved from the Supabase function we cache the image
in the browser via the cache control headers. If the image is directly
retrieved from it's url it's cached by the "CachedNetworkImage" widget.
