Add LDAP authentication

[cbaker6]

• add ParseLDAP
• Documentation
• Tests
• Fixed a bug that would have prevented unlinking new auths and accidentally unlinking the Apple auth

[codecov]

Codecov Report

Merging #79 (7053918) into main (ffa070f) will decrease coverage by 0.01%.
The diff coverage is 77.10%.

@@            Coverage Diff             @@
##             main      #79      +/-   ##
==========================================
- Coverage   79.13%   79.11%   -0.02%     
==========================================
  Files          62       63       +1     
  Lines        4936     5018      +82     
==========================================
+ Hits         3906     3970      +64     
- Misses       1030     1048      +18     

Impacted Files	Coverage Δ
...rseSwift/Authentication/3rd Party/ParseApple.swift	75.64% <ø> (ø)
...arseSwift/Authentication/3rd Party/ParseLDAP.swift	75.64% <75.64%> (ø)
...Authentication/Protocols/ParseAuthentication.swift	73.73% <100.00%> (+1.10%)	⬆️
Sources/ParseSwift/Objects/ParseObject.swift	76.23% <0.00%> (+0.28%)	⬆️

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[cbaker6]

@TomWFox can you check the docs on this one?

[cbaker6]

Followed the process in #55

[TomWFox]

Docs LGTM 👍