This makes it easier to maintain per-institution hacks that start
interacting with each other if you try to do them all in the same client
code. This commit also breaks out the existing Vanguard hack into its
own Client implementation.
This adds a python script to generate constants.go when `go generate` is
called, and updates the structs, tests, and command-line client to all
use the new named constants.
This removes the many decodeXXXMessageSet() functions and replaces them
with a large map and a single generic decodeMessageSet() function. Also
change Responses to satisfy the Message interface as pointer types
(instead of the raw types), add the full set of top-level message sets
(though most of them still lack any message-parsing ability), adjust the
message set names to more closely mirror their OFX names, and fixup
tests and the command-line client to match the above changes.
This allows encoding/xml to properly comparison against nil to see if
they should be marshalled if the 'xml' tag contains ",omitempty" and for
users to test against nil to see if a field was present in the parsed
OFX.
This commit also fixes up cmd/ofx to use the new pointers.
