Eclipse Californium (Cf) CoAP Framework 2.6.3

Bugfix Release:

• d77fa2d76 2021-04-29 Remove not longer used property from pom.
• 908bfd27b 2021-04-23 Remove redundant getCertificateChain() call.
• fb5b4bc8a 2021-04-16 Fix charset conversion in proxy2.
• f6b7517bd 2021-04-15 Fix ExecutorsUtil's and Request's javadoc.
• 53b16da47 2021-03-31 OSCORE: Updates the functionality for securely re-generating contexts
• 07e864263 2021-04-04 Fix race condition in unit test.
• d4e922586 2021-04-04 Fix ssl context util using older android version.
• fba273a35 2021-03-30 Use MDC optional.
• 48917dd4c 2021-03-30 Fix common dummy value for missing package version.
• 5e8540abb 2021-03-29 Fix missing package information.
• be0bd796b 2021-03-27 Fix code smells.
• f80a778a3 2021-03-23 Fix logging arguments.
• 323052d66 2021-03-24 Fix code smells and minor bugs.