This more strongly types the ubiquitous message id type by no longer
making it an integer. It keeps the actual ID opaque. Only for the
generic job API the number keeps being used. Some locations also need
to create it from an integer and call MsgId::new().
Turns out that anyone that uses these either justs wants a file or
wants a blob. Consolidate those patterns into one place and simplify
all the callers.
This creates a specific type for blobs, with well defined conversions
at the borders. It also introduces a strong type for the Param::File
value since that param is often used used by the public API to set
filenames using absolute paths, but then core changes the param to a
blob before it gets to the database.
This eliminates a few more functions with very mallable C-like
arguments behaviour which combine a number of operations in one.
Because blob filenames are stored so often in arbitrary strings this
does add more code when receiving those, until the storage is fixed.
File name sanitisation is now deletated to the sanitize-filename crate
which should do a slightly better job at this.
if the past we had lots of crashes because of unexpected unwrap failures,
mostly related to string.
this commit avoids them eg. for string-conversions that may panic
eg. when encountering a null-byte or by logical programming errors
where an object is assumed to be set but is not under unexpected circumstances.
