This commit modifies the NewPayloadFromReader to apply known
presence/omission contraints in the event that the tlv parser returns an
unknown required type failure.
Now that the parser has been modified to finished parsing the stream to
obtain a proper parsed type set, we can accurately apply these higher
level validation checks. This overrides required type failures, such
that they are only returned if the sender properly abided by the
constraints on fields for which we know.
The unit tests are updated to create otherwise valid payloads that then
return unknown required type failures. In one case, a test which
previously returned an unknown required type failure is made to return
an included failure for the sid, indicating the unknown required type 0
is being overruled.
This commit adds a hop.PayloadViolation enum which encompasses the cases
where the sender omits, includes, or requires a type that causes an
ErrInvalidPayload faiulre.
The existing Omitted bool is converted to this PayloadViolation, and
NewPayloadFromReader is updated to return such a failure with a
RequiredViolation when an unknown required type is detected.
The unit tests are updated to cover the three possible cases of
RequiredViolations, as well as included valid intermediate and final hop
tests.
From BOLT 04:
The writer:
- MUST include amt_to_forward and outgoing_cltv_value for every node.
- MUST include short_channel_id for every non-final node.
- MUST NOT include short_channel_id for the final node.
