chore(backend): Update ldap3 requirement from >=2.9.0 to >=2.9.1 in /backend

[dependabot]

Updates the requirements on ldap3 to permit the latest version.

Changelog

Sourced from ldap3's changelog.

2.9.1 - 2021.07.18

- new feature: added support for using Kerberos authentication on windows clients using the native winkerberos library
- new feature: added support for using Channel Bind tokens with Kerberos authentication on windows clients
- fixed a bug related to using start_tls with a RESTARTABLE strategy that caused errors to be raised erroneously.
- fixed a bug around the type checking of Reverse DNS Settings with Kerberos authentication
- fixed an issue related to decoding unicode strings in LDAP referrals and attributes in python 2
- minor documentation updates and corrections

2.9 - 2021.01.24

- new feature: SafeRestartable strategy (SAFE_RESTARTABLE) for using a restartable Connection object in a multi-threading program
- tested against Python 3.9
- added requirements-dev.txt
- fixed logging unicode exceptions in python2.7
- added more granular control over use of reverse dns with Kerberos (thanks Azaria)
- support MS Active Directory persistent search (thanks eLeX)
- added support for LDAP signing when using DIGEST-MD5 authentication (thanks Augustin-FL)
- check only for searchResEntries in LDIF conversion (thanks Jay)
- modify-increment now works properly in mock strategies (thanks Saint-Marcel)
- objectGUID are now converted properly (thanks Janne)
- default timeout in asynchronous strategies raised to 20 seconds

2.8.1 - 2020.09.07

- fixed regression in 2.8 for members returned in AD auto-range search (thanks Felix)
- fixed regression in 2.8 for attribute error in restartable class (thanks Christian)
- try to use Crypto library if present for hashing NTLM password on python interpreter missing the MD4 OpenSSL algorithm (thanks Doron)

2.8 - 2020.08.08

- new feature: SafeSync strategy (SAFE_SYNC) for using a synchronous Connection object in a multi-threading program
- new feature: LDIF_LINE_LENGTH for specifying line length wrapping in ldif-content output (default to 78 as per RFC 2849)
- fixed requirements for pyasn1
- fixed regression for ldapi connections
- fixed issue with lazy connection requesting server info on every operation
- fixed searching by objectGUID in hex format (thanks Matt)
- added iso_format parameter to utils.format_json to return dates in ISO format (thanks Hugh)
- fixed issue with Referral attributes not returned by the referral server (thanks Nazarii)
- fixed lost error message in auto_bind (thanks cfelder)
- fixed delete_old_dn in mock connections (thanks kpinc)
- fixed a ResourceWarning with lazy connections
- fixed entry_to_json() that in python2 modified the original entry value (thanks Dirk-Jan)
- tests doesnt' raise Exception if real server is not present (thanks Matej)

2.7 - 2020.03.01

- tested against Python 3.8.1 and pyasn1 0.4.8
- re-enabled ssl exception raising on bad certificate when only 1 server is present in the server pool
- removed Python 2.6 from Travis configuration (thanks gliptak)
- added support for source specifications in LDAP connections (thanks Azaria)
- added support for allowing special AD security identifier (SID) in DN (thanks John)
- fixed pickling of entry and attribute (thanks cfelder)
- close connection when auto_bind fails (thank Hrishikesh)
- operational attributes can be used in Abstraction Layer (thanks Sohalt)

... (truncated)

Commits

• 3a2f896 Merge pull request #971 from cannatag/update-changenotes
• 21cf37a Updated the changelog for v2.9.1
• 05f1a16 prepared for 2.9.1
• ce4c7bb Merge pull request #967 from cannatag/fix-reverse-dns-again
• a7ec261 Merge pull request #968 from cannatag/fix-restart-tls
• d0d1b25 Merge pull request #969 from cannatag/fix-unicode-py2
• 7718844 Fix issues with unicode strings in python 2.
• ea50731 Fix a small logic bug on restarting StartTLS
• 2832895 Changed the check for reverse dns settings to use a supported
• 6e25d5c Merge pull request #956 from cannatag/fix-posix-check
• Additional commits viewable in compare view

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