ensure integrity values of notifications are base64 encoded

[tomkralidis]

Users have reported that some notification messages properties.integrity.value values are not base64 encoded (per the WNM draft), even though they should be. Relevant reference implementations (wis2box, pywis-pubsub) should be updated accordingly.

Many thanks to @allanfrankwork for reporting the issue.

cc @kaiwirt @golfvert

[tomkralidis]

Relevant updates/fixes:

• ensure notification message integrity is encoded as base64 wis2box#484
• fix data verification, add utility, tests pywis-pubsub#28
• add explicit contentEncoding for properties.integrity.value wis2-notification-message#55

[tomkralidis]

Updates:

• pywis-pubsub 0.5.0 released: https://github.com/wmo-im/pywis-pubsub/releases/tag/0.5.0
• wis2box fix will be part of 1.0b5 release

[kaiwirt]

For GC Offenbach and WIS2 Node Offenbach we use the base64 encoding. However we also see WNM without this encoding. Input-wise we support both hex and base64

[golfvert]

To be closed.