clarify WNM major version change requirement

[tomkralidis]

Clarify that a major change to WNM would propagate a major version change to WTH.

[tomkralidis]

After further discussion with @josusky, it is proposed to defer until initial publication of WNM. As a result:

• open a new issue for post INFCOM discussion
• update this PR to remove the Requirement

[antje-s]

What are the reasons for removing the requirement?
In my view, the WTH version change is important for major changes in the notification content so that subscribers can check that the new payload can be processed correctly and completely or can make the necessary adjustments to their implementation

[antje-s]

Updates in REQ_versioning.adoc are ok

[josusky]

(Commenting once again using the right account):

What are the reasons for removing the requirement?
Maybe Tom can paste here the whole discussion, but the main points are:

Change of the WNM (notification format) is very unlikely in the near future.
We do not have an agreed migration strategy for such change (it can leverage change of WTH version but not necessary).
There might be some other situations when change of the WTH will be needed but perhaps instead of trying to enumerate all possible situations as SHALLs we could add a permission (MAY) to change the version number - for good reason and with appropriate advance notification.
No need solve this in the current version of the specification.
However, we should add this into agenda for a team meeting after the INFCOM-3.

[josusky]

As already mentioned, this needs more discussion. Strong relation between WNM version change and WTH version is not justified at the moment.

[amilan17]

@tomkralidis are we removing this requirement entirely? Or keeping the revisions as proposed in this PR?