The primary aim of this commit is to reduce confusion between
'content::Json' and 'rocket::serde::json::Json' be renaming the former
to 'content::RawJson'. The complete changes in this PR are:
* All responders in the 'content' module are prefixed with 'Raw'.
* The 'content::Custom' responder was removed entirely.
* The 'Plain' responder is now 'RawText'.
* The 'content' API docs point to the 'serde' responders.
* The docs and examples were updated accordingly.
'Missing' allows constructing a 'FileServer' even if the supplied path
does not exist. 'IndexFile' allows serving a single file as the index of
the mount path.
This allows responses to be sent to the client even when data is only
partially read, significantly improving the experience for the client
from one with a "connection closed" error to one with a proper response.
The consequence is a lifetime in 'Data'.
Though other non-lifetime-introducing solutions exist, the introduction
of a lifetime to 'Data' is a longstanding desire as it prevents
smuggling 'Data' into a longer-lived context. Use of 'Data' in that
context was unspecified with various runtime consequences. The addition
of a lifetime bound by the request prevents this error statically.
In summary, the changes are:
* Clients receive responses even when data isn't fully read.
* 'Data' becomes 'Data<'r>'. 'FromData' changes accordingly.
* Route 'Outcome's are strictly tied to the request lifetime.
Tangentially, the invalid length form field validation error message has
improved to format length in byte units if it exceeds 1024.
This changes 'TempFile' doctests so that different file names are used
across them, avoiding race conditions where one test deletes a file
another test just created and thus expects to subsequently exist.