init setContentDisposition and setContentType functions immediately as
private functions to reduce complexity
so instead check for the required map/store before using them
also fixed content-type override ending up with duplicate headers
both headers cannot co-exist at the same time, so we pass the expected
content-length value into 2nd param of Response.stream(), so that the
internal can decide to add it only when required
also moved it from middlewares to handlers directory
reasoning is that this class is better suited to handle routes directly
instead of being a global middleware
since IO stat to check if request path matches a physical file in the
disk every single time is not very performant
this required expanding our custom error classes with support for
arbitrary internal api error codes
however it'll only be used for invalid token errors for now (10001)
no plan to assign codes to other existing api errors
at that point it's probably better to redo the whole api infrastructure
ClientError will default to 400 HTTP error code.
ServerError will default to 500 HTTP error code.
Following the previous commit, these for now are only being used in
albumsController. More will soon follow.
Additionally fixed existing album names can sometimes be re-used when
editing an album.
This will be used for errors that are to be delivered to users, AND not
to be logged into the server (as in it stacktraces and all).
This will eventually remove the need to throw string literals.
In this commit, this has only been implemented on albumsController.js,
but more will soon to come.
