Prelogin and Login handling for TDS74 FederatedAuth with Security Token

[bowleri]

Fixes #135

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.37572% with 8 lines in your changes missing coverage. Please review.

Project coverage is 89.19%. Comparing base (585547b) to head (ea3f618).

Files	Patch %	Lines
src/pytds/tds_session.py	95.18%	4 Missing :warning:
tests/all_test.py	33.33%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #166 +/- ## ========================================== + Coverage 89.10% 89.19% +0.09% ========================================== Files 44 44 Lines 8095 8240 +145 ========================================== + Hits 7213 7350 +137 - Misses 882 890 +8 ```

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[bowleri]

Appveyor update of ruff from ruff-0.5.1 to ruff-0.5.3 has created failures in tds_types.py

[denisenkom]

Hi @bowleri, thank you for this pull request. I have some questions below.

How can I test this? Maybe you can give me a simple example script that generates access token and nonce, that I could then use against my test Azure account.

It also seems couple validations are missing, can you add those validations?:

• It should fail connection attempt if access_token was provided but server is not supporting TDS 7.4
• It should fail if access_token was provided but contained an empty string

I noticed that you convert access_token into ASCII byte string, this assumes that access_token contains only ASCII characters. Is this assumption safe?