Added new API errors for LDAP

[taran-p]

Community Contribution License

All community contributions in this pull request are licensed to the project maintainers
under the terms of the Apache 2 license.
By creating this pull request I represent that I have the right to license the
contributions to the project maintainers under the Apache 2 license.

Description

Adds API errors:
If LDAP is not enabled with an LDAP command
If LDAP short username is expected but DN is given

Uses these in the code

Motivation and Context

Currently these known errors return as internal errors

How to test this PR?

mc idp ldap accesskey create with LDAP not enabled, with incorrect username, or with a DN
mc idp ldap policy attach/detach with LDAP not enabled

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimization (provides speedup with no functional changes)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Fixes a regression (If yes, please add commit-id or PR # here)
• Unit tests added/updated
• Internal documentation updated
• Create a documentation update request here

[vadmeste]

LGTM