Implement XEP-0448: Encryption for stateless file sharing parsing

[lnjX]

• esfs
• esfs: Implement parsing
• Implement serialization
• Add rule of six constructor

PR check list:

• [x] Document your code
• [x] Add \since QXmpp 1.X, QXMPP_EXPORT
• [x] Fix doxygen warnings (see log when building with -DBUILD_DOCUMENTATION=ON)
• [x] Update doc/doap.xml
• [x] Add unit tests
• [x] Format the code: Run clang-format -i src/<edited-file(s)> tests/<edited-file(s)>

[codecov[bot]]

Codecov Report

Merging #463 (c044a51) into master (50be942) will increase coverage by 0.07%. The diff coverage is 82.65%.

:exclamation: Current head c044a51 differs from pull request most recent head f380c52. Consider uploading reports for the commit f380c52 to get more accurate results

@@            Coverage Diff             @@
##           master     #463      +/-   ##
==========================================
+ Coverage   68.63%   68.71%   +0.07%     
==========================================
  Files         275      277       +2     
  Lines       23905    24016     +111     
==========================================
+ Hits        16407    16502      +95     
- Misses       7498     7514      +16     

Impacted Files	Coverage Δ
src/base/QXmppEncryptedFileSource.cpp	79.51% <79.51%> (ø)
src/base/QXmppEncryptedFileSource_p.h	100.00% <100.00%> (ø)
src/base/QXmppHash.cpp	33.68% <100.00%> (-0.36%)	:arrow_down:
tests/qxmppmessage/tst_qxmppmessage.cpp	94.84% <100.00%> (+0.17%)	:arrow_up:
tests/util.h	86.27% <0.00%> (ø)
src/base/QXmppBitsOfBinaryData.cpp	100.00% <0.00%> (ø)
...ts/qxmppbitsofbinaryiq/tst_qxmppbitsofbinaryiq.cpp	100.00% <0.00%> (ø)
tests/qxmppomemodata/tst_qxmppomemodata.cpp	98.25% <0.00%> (+<0.01%)	:arrow_up:
src/base/QXmppHttpFileSource.cpp	66.66% <0.00%> (+13.33%)	:arrow_up:

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