Validation errors for feature vectors.

Validate a feature vector for local use (vectors we create/send).

Checks:

• No feature has both optional and required bits set
• All set features are valid for the given context
• All dependencies of set features are also set
• C- context forces odd bits only, C+ forces even bits only

>>> import Data.Maybe (fromJust)
>>> import Lightning.Protocol.BOLT9.Codec (setFeature)
>>> let mpp = fromJust (featureByName "basic_mpp")
>>> let ps = fromJust (featureByName "payment_secret")
>>> validateLocal Init (setFeature mpp False empty)
Left [MissingDependency "basic_mpp" "payment_secret"]
>>> validateLocal Init (setFeature mpp False (setFeature ps False empty))
Right ()

Validate a feature vector received from a remote peer.

Checks:

• Unknown odd (optional) bits are acceptable (ignored)
• Unknown even (required) bits are errors
• If both bits of a pair are set, treat as required (not an error)
• Context restrictions still apply for known features

>>> import Lightning.Protocol.BOLT9.Codec (setBit)
>>> validateRemote Init (setBit 999 empty)  -- unknown odd bit: ok
Right ()
>>> validateRemote Init (setBit 998 empty)  -- unknown even bit: error
Left [UnknownRequiredBit 998]

Find the highest set bit in a feature vector.

Returns Nothing if the vector is empty or has no bits set.

Collect all set bits in a feature vector.

Returns a list of bit indices in ascending order.