Add Graph credentials cache and fix issue with batch size

[nathanthorpe]

Should resolve #333 and #330

• Add the ability to cache credentials from Graph (useful for the DeviceCode flow where you don't want to log in each time). This could probably deprecate the UsernamePassword flow since the other two are more ideal and work with MFA
• Add the batch_size arg into fetch_messages method since Graph defaults to only returning 10 messages
• Fix access denied error if using DeviceCode flow and connecting to a shared mailbox with a different account.
• Fix gmail configuration properties on readme and package requirement

[codecov[bot]]

Codecov Report

Merging #334 (d4e7bd6) into master (315b99f) will decrease coverage by 0.57%. The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master     #334      +/-   ##
==========================================
- Coverage   60.39%   59.81%   -0.58%     
==========================================
  Files           8        8              
  Lines        1280     1299      +19     
==========================================
+ Hits          773      777       +4     
- Misses        507      522      +15     

Impacted Files	Coverage Δ
parsedmarc/__init__.py	62.36% <0.00%> (ø)
parsedmarc/mail/graph.py	25.00% <26.08%> (-0.72%)	:arrow_down:
parsedmarc/mail/gmail.py	35.71% <100.00%> (ø)
parsedmarc/mail/imap.py	41.02% <100.00%> (ø)
parsedmarc/mail/mailbox_connection.py	58.82% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 315b99f...d4e7bd6. Read the comment docs.

[fluidum]

For me batch_size = 0 under [mailbox] neither [msgrpah] block didn't work. Maximum I've got working was 1000 and under [mailbox]. I shared my working example on 8.3.2 version here: https://github.com/domainaware/parsedmarc/issues/365#issuecomment-1293363572