- echo is now on v4 with major changes including a few breaking changes
- bind() behaviour is now strict. JSON / form etc. unmarshalling of
request data need appropriate `json`, `form` tags. Missing tags for
the public subscription page is added in this commit.
- This also closes#602.
While file content (MIME) check already existed, the lack of file
extension check allowed arbitrary extensions to be uploaded and
then accessed via the static file server. For instance, a .html file
with JPG content intersperesed with Javascript.
This commit adds a file extension check on top of the MIME type check.
