We only want two statuses for expense: not yet paid (pending), and paid.
Thus, it is a bit different from quotes and invoices, because expenses
do not pass throw the “workflow” of created→sent→{pending,paid}. That’s
way in this case the status field is already in the new expense form,
instead of hidden, and by pending is not equivalent to created but
unpaid (i.e., the same status color).
With the new select field in the form, the file field no longer can
span two columns or it would be alone on the next row.
Closes#67.
I had to change MethodOverrider to check whether the form is encoded as
multipart/form-data or i would not be able to get the method field from
forms with files.
For now i add the file manually, i.e., outside add_expense and
edit_expense PL/pgSQL functions, because it was faster for me, but i
will probably add an attach_to_expense function, or something like that,
to avoid having the whole ON CONFLICT logic inside Golang—this belongs
to the database.