Autobahn

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* fix: Twisted v21.2.0 breaks Crossbar.io (see https://github.com/crossbario/crossbar/issues/1864)

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* new: use_binary_hex_encoding option for JSON object serializer
* fix: correct some sphinx doc references
* new: minimum supported Python (language) version is now 3.7 (on CPython and PyPy)
* new: more XBR proxy/stub code generation capabilities (RPC call/invoation handlers)
* fix: wamp-cryptosign loading of keys from SSH agent
* fix: update Docker image building and build Docker multi-arch images
* new: add more WAMP-cryptosign signature test vectors and unit tests
* fix: include XBR code rendering templates in package manifest

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* new: XBR ABI files now via separate package ("xbr") - substantially reduce package size for non-XBR users
* fix: circular dependency in "xbr" install flavor (prohibited pip install from github master)
* fix: XBR package manifest and CLI user profile loading

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* fix: consider 'wamp.close.goodbye_and_out' a clean exit (1450)
* fix: HASH import as well as improve diagnostics if things go wrong (1451)
* fix: add missing jinja2 dependency for XBR CLI (1447)
* fix: ``wamp.close.goodbye_and_out`` counts as a clean exit (1370)

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* fix: URL must be re-encoded when doing redirect (1439)
* fix: update and migrate CI/CD pipeline to GitHub Actions
* new: minimum supported Python (language) version is now 3.6 (on CPython and PyPy)

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* fix: derive_bip32childkey traceback (1436)
* fix: update and adjust docker files to upstream changes