Restore Azure Blob Storage + ID-attribute docs, fix nav description (#9096)

* Restore Azure Blob Storage docs and fix nav description

PR #8976 (merged for v11.9.0) was accidentally reverted by the "V11.8
Docs" merge (#8974), which removed both the azure-blob-storage.rst
walk-through page and the Azure sections in
environment-configuration-settings.rst. This restores that content and
adds the nav entry with corrected, action-oriented wording.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01739QHYVMKh6R81gcqEfGgP

* Add Azure Blob Storage page to the hidden toctree

The bullet-list entry alone isn't enough for Sphinx to include the
page in the nav sidebar; it also needs to be listed in the toctree
directive, which was dropped by the same revert.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01739QHYVMKh6R81gcqEfGgP

* Restore ID attribute case-sensitivity notes

PR #9020 was accidentally reverted from master by the "V11.8 Docs"
merge (#8974), which removed the case-sensitivity notes for the
AD/LDAP ID attribute, AD/LDAP Group ID attribute, and SAML ID
attribute settings.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01739QHYVMKh6R81gcqEfGgP

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: amyblais

source/administration-guide/configure/authentication-configuration-settings.rst

@@ -821,6 +821,9 @@ ID attribute
 .. note::
   If a user's ID Attribute changes, a new Mattermost account is created that is not associated with the previous account. If you need to change this field after users have signed-in, use the :ref:`mmctl ldap idmigrate <administration-guide/manage/mmctl-command-line-tool:mmctl ldap idmigrate>` command.
 
+.. note::
+  The ID attribute value is matched verbatim - Mattermost applies no case normalization. With PostgreSQL's default case-sensitive collation, a change in casing is treated as a new user and a separate account is created. Ensure your AD/LDAP server returns this attribute with consistent casing.
+
 .. config:setting:: login-id-attribute
   :displayname: Login ID attribute (AD/LDAP > Account Synchronization)
   :systemconsole: Authentication > AD/LDAP
@@ -1029,6 +1032,9 @@ Group ID attribute
 .. note::
   This attribute is only used when AD/LDAP Group Sync is enabled and it is **required**.  See the :doc:`AD/LDAP Group Sync documentation </administration-guide/onboard/ad-ldap-groups-synchronization>` for more information.
 
+.. note::
+  The Group ID attribute value is matched verbatim - Mattermost applies no case normalization. With PostgreSQL's default case-sensitive collation, a change in casing means Mattermost no longer recognizes the previously synced group and treats it as a new, unlinked group. Ensure your AD/LDAP server returns this attribute with consistent casing.
+
 Synchronization performance
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -1555,6 +1561,9 @@ Id attribute
 | String input.                                                                                                        | - Environment variable: ``MM_SAMLSETTINGS_IDATTRIBUTE``      |
 +----------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------+
 
+.. note::
+  The ID attribute value is matched verbatim - Mattermost applies no case normalization. With PostgreSQL's default case-sensitive collation, a change in casing is treated as a new user and a separate account is created. Ensure your identity provider returns this attribute with consistent casing.
+
 .. config:setting:: guest-attribute
   :displayname: Guest attribute (SAML)
   :systemconsole: Authentication > SAML 2.0