Add username as an option for SearchFilter

[kirktarou]

Currently, search filter substitutions are limited only to the bindPrincipal (username@domain).
'username' value will be substituted with {1}

[aabeling]

This seems to be a solution for #3303

[pivotal-issuemaster]

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[pivotal-issuemaster]

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[pivotal-issuemaster]

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[jgrandja]

@Kirkalicious Thanks for submitting this PR. The search filter substitution for {1} won't take effect based on your changes as the default searchFilter in ActiveDirectoryLdapAuthenticationProvider is set at

(&(objectClass=user)(userPrincipalName={0}))

We also need tests added for this change. After you update the PR I'll merge this.

Thank you.

[jgrandja]

Related to #3950

[jgrandja]

Thanks for submitting this PR @Kirkalicious.

We are currently re-thinking our approach to an Active Directory AuthenticationProvider implementation. Our direction is to deprecate ActiveDirectoryLdapAuthenticationProvider and leverage the existing LdapAuthenticationProvider and provide a custom strategy of LdapAuthenticator for Active Directory.

The work has already started in #4064 if you would like to track the progress and provide any input/feedback.

I'm going to close this PR as we will address your input/feedback in #4064.
Thank you.