The specification states that the server can cancel observations "at any
moment, by sendinga GET request with Observe option=1, the LwM2M Server
cancancel an “Observe”operation on a specified Resource, or specified
Object Instance(s)."
It does not mention any token matching requirement, but RFC 7641 does.
The correct interpretation is not obvious. The EMQx LwM2M implementation
uses a new token for instance, which does not work with Zephyrs token
matching cancel-observe.
This commit introduces cancel-observe via path matching as a Kconfig
option. This could hypothetically introduce problems when we are
connected to multiple peers simultaneously, but since that is not likely
to be supported for a long time (if ever), this change should be fairly
uncontroversial since path matching is only used as a fallback.
Signed-off-by: Benjamin Lindqvist <benjamin.lindqvist@endian.se>
e3f8757b70