Fixed #12331: Change the way userDn is build for non-AD login

[P-EB]

Currently, snipe-it relies on a manually crafted user DN to bind a user and therefore check if they exist, and then, it searches in LDAP if the user is found when applying the filter.

This works nicely when the base_dn is "fixed". In a company with multiple business lines or business units, though, there might be more than one OU for LDAP users, and in that case, crafting the DN manually might fail.

This patch aims at crafting the userDn from a ldap_search, assuming the user field is unique. If more than 1 user is found, the user field is not unique and the login method will throw.

This increases significantly the LDAP login flexibility.

Fixes #12331

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Tested on our stage SnipeIT server.

Test Configuration:

• PHP version: 8.1
• MySQL version: MariaDB 10.3.39
• Webserver version: nginx 1.14.2, snipeIT latest version
• OS version: Debian 10

Checklist:

• I have read the Contributing documentation available here: https://snipe-it.readme.io/docs/contributing-overview
• I have formatted this PR according to the project guidelines: https://snipe-it.readme.io/docs/contributing-overview#pull-request-guidelines
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

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[what-the-diff]

PR Summary

• Enhanced Search Functionality for LDAP Users
  The team has incorporated additional logic to improve how the system finds and links to LDAP (Lightweight Directory Access Protocol) users. This enhancement offers more efficiency and accuracy in identifying user profiles in the network.

• Revised Filter Query
  The filter query, which is used to sort and sift through data, has been modified for better data handling, further streamlining the process of looking up information.

• Introduction of Logging
  New logging functionality has been added. This new feature will track events and errors, providing a valuable tool for troubleshooting and system maintenance, thereby reducing downtime and inefficiencies.

[uberbrady]

I took a swing at re-implementing this functionality here: #17832 - does this doe the same trick for you?