This commit changes the listinvoices and lookupinvoice endpoints to
avoid collisions when making requests.
We can still retrieve a list of pending invoices with `listinvoices` by
appending the parameter `pending_only=true` to the request URL.
When accessing a value from a byte slice, the value is returned as a
byte, which is just a uint8. When the first byte takes more than 3 bits
of space, shifting 5 bits left results in data loss.
This commit allows parseRoutingInfo to return an error when parsing a
routing info field whose length is not a multiple of 51 bytes, rather
than crash.
This commit refactors parsing each of the tagged fields of an invoice
into their own method. This makes the code easier to read and will allow
us to introduce unit tests for each parsing method.
Wilmer Paulino