Add the SCRAM mechanism.

[ChadSikorra]

Adding SCRAM support since DIGEST-MD5 is long since dead / unsupported. Adding SASL support server side to the LDAP library. But is also nice to support this from the client side.

Additionally adding some markdown doc.

[codecov]

Codecov Report

❌ Patch coverage is 97.74920% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.80%. Comparing base (75db064) to head (6746e74).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/FreeDSx/Sasl/Challenge/ScramChallenge.php	97.46%	6 Missing ⚠️
src/FreeDSx/Sasl/SaslPrep.php	94.73%	1 Missing ⚠️

❌ Your project status has failed because the head coverage (78.80%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##             master       #5      +/-   ##
============================================
+ Coverage     72.81%   78.80%   +5.99%     
- Complexity      354      428      +74     
============================================
  Files            21       25       +4     
  Lines           982     1293     +311     
============================================
+ Hits            715     1019     +304     
- Misses          267      274       +7     

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[Neustradamus]

@ChadSikorra: Thanks a lot for your work about SCRAM and tls-unique support!

Can you specify that DIGEST-MD5 and CRAM-MD5 are not secure and must not be used?

Important about TLS Channel Binding:

• tls-unique is for TLS 1.2 and before
• tls-server-end-point is for TLS 1.3 and TLS 1.2 and before
• tls-exporter is for TLS 1.3

You can see @fabiang sasl project here:

• https://github.com/fabiang/sasl
• https://github.com/fabiang/sasl/issues

Another projects where SCRAM supports have been done by @schengawegga:

• https://github.com/pear/Auth_SASL
• https://github.com/pear/Auth_SASL2
• https://github.com/pear/Net_SMTP

It will be nice to talk all together about the PHP problem and to show that it is really important to have an improvement in PHP core:

• https://github.com/php/php-src/issues/ 16766

Linked to:

• SCRAM-SHA-1(-PLUS) + SCRAM-SHA-256(-PLUS) + SCRAM-SHA-512(-PLUS) + SCRAM-SHA3-512(-PLUS) supports #3
• Add the SCRAM mechanism. #5
• State of Play scram-sasl/info#1