Allow to mark messages as read

A new feature introduced in briar!1285.

Fixes #18
3 jobs for 18-mark-read in 1 minute and 57 seconds (queued for 56 seconds)
Status Job ID Name Coverage
  Test
passed #6080
pycodestyle

00:00:37

failed #6081
pylint

00:00:41

passed #6082
pytest

00:00:38

93.0%
 
Name Stage Failure
failed
pylint Test
Successfully installed MarkupSafe-1.1.1 astroid-2.4.2 attrs-20.2.0 certifi-2020.6.20 chardet-3.0.4 coverage-5.3 idna-2.5 importlib-metadata-2.0.0 iniconfig-1.0.1 isort-5.5.3 lazy-object-proxy-1.4.3 mako-1.1.3 markdown-3.2.2 mccabe-0.6.1 more-itertools-8.5.0 packaging-20.4 pdoc3-0.9.1 pluggy-0.13.1 py-1.9.0 pycodestyle-2.6.0 pylint-2.6.0 pyparsing-2.4.7 pytest-6.0.2 pytest-cov-2.10.1 pytest-mock-3.3.1 requests-2.24.0 requests-mock-1.8.0 requests2-2.16.0 six-1.15.0 toml-0.10.1 typed-ast-1.4.1 urllib3-1.21.1 websockets-8.1 wrapt-1.12.1 zipp-3.2.0
$ tools/tests/test-pylint.sh
************* Module briar_wrapper.models.private_chat
briar_wrapper/models/private_chat.py:54:4: C0103: Argument name "messageId" doesn't conform to snake_case naming style (invalid-name)

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Your code has been rated at 9.96/10

ERROR: Job failed: exit code 1