Implement admin JWT cookie, separate JWT issuers for each type of token and migrate admin page to handlebars template

Bump the vault version used to the latest one

Add Feature-Policy header

(https://doc.rust-lang.org/stable/std/primitive.i64.html#method.to_be_bytes)

Fix sharing the item to organization.

Default to $data_folder/templates and remove dev option (use `TEMPLATES_FOLDER=src/static/templates` instead)

Disallow users from accepting invitation twice