Eclipse Californium (Cf) CoAP Framework 2.6.2

Bugfix Release:

• 559969103 2021-03-17 Fix removing handshake messages while iterating over list.
• d9749219d 2021-03-15 Fix con-notify race-condition.
• b8f9a0113 2021-03-15 Suppress duplicates, if messages are not sent.
• 6d4eb6869 2021-03-15 Fix deduplication of notifies.
• 8ce437cf5 2021-03-08 Update eclipse-jarsigner-plugin to 1.1.5.
• 578972574 2021-02-27 Fix connection's expect cid.
• e00f9c7d2 2021-02-09 Add Ed25519/Ed448 support for raw-public-key identities.
• 74a262f30 2021-02-09 Add null as return value for payload.
• db56e8a0d 2021-02-04 Update sandbox URL to californium.eclipseprojects.io