Add black formatting in tox + rev ignore in git blame

As part of our effort to standardize our project repos, we are adding
black formatting to freshmaker in tox.

This commit:
    - adds a step with `black --check` in tox, to verify the code is
      well formatted
    - adds a `.git-blame-ignore-revs` file to keep track of large
      reformatting commits that should be ignored by `git blame`
    - adds instructions on how to use `.git-blame-ignore-revs`
      automatically in a local environment

For more information, please see the following links:
https://stackoverflow.com/questions/34957237/can-i-configure-git-blame-to-always-ignore-certain-commits-want-to-fix-git-blam/57129540#57129540
https://akrabat.com/ignoring-revisions-with-git-blame/
https://docs.github.com/en/repositories/working-with-files/using-files/viewing-a-file#ignore-commits-in-the-blame-view

JIRA: CWFHEALTH-2279

.git-blame-ignore-revs

@@ -0,0 +1,7 @@
+# Have a look at
+# https://stackoverflow.com/questions/34957237/can-i-configure-git-blame-to-always-ignore-certain-commits-want-to-fix-git-blam/57129540#57129540
+# https://akrabat.com/ignoring-revisions-with-git-blame/
+# https://docs.github.com/en/repositories/working-with-files/using-files/viewing-a-file#ignore-commits-in-the-blame-view
+
+# Run code through black for formatting
+84635e2dd3fd26f1c63ff50c854890a9d04e83b3

README.md

@@ -120,3 +120,23 @@ python -m pip install pip-tools
 ```
 
 more info available at: https://github.com/jazzband/pip-tools/
+
+
+# Ignoring large reformattings with git blame
+
+The commits listed in `.git-blame-ignore-revs` are automatically ignored in github blame view
+(https://docs.github.com/en/repositories/working-with-files/using-files/viewing-a-file#ignore-commits-in-the-blame-view).
+This feature is meant to ignore commits that just introduced reformatting, and maintain the logical
+contributions of each line.
+
+You can make use of the `.git-blame-ignore-revs` file locally by passing it as an argument to the
+blame command:
+```
+git blame --ignore-revs-file .git-blame-ignore-revs ...
+```
+or by adding it to your local git configurations:
+```
+git config --local blame.ignoreRevsFile .git-blame-ignore-revs
+```
+Note that this should be done for per-project, as some projects may lack the `.git-blame-ignore-revs`
+file, and in this case `git blame` would return an error.

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = bandit, docs, flake8, mypy, py311
+envlist = bandit, docs, flake8, black, mypy, py311
 ignore_base_python_conflict = True
 
 [testenv]
@@ -30,6 +30,11 @@ skip_install = true
 deps = flake8
 commands = flake8
 
+[testenv:black]
+basepython = python3
+deps = black
+commands = black --line-length 100 --check freshmaker tests --exclude freshmaker/migrations/
+
 [testenv:mypy]
 description = type check
 deps =