Docs: Example for multiple LDAP servers (#17216)

Fixes #16898

docs/sources/auth/ldap.md

@@ -215,6 +215,67 @@ email =  "email"
 # [[servers.group_mappings]] omitted for clarity
 ```
 
+### Multiple LDAP servers
+
+Grafana does support receiving information from multiple LDAP servers.
+
+**LDAP specific configuration file (ldap.toml):**
+```bash
+# --- First LDAP Server ---
+
+[[servers]]
+host = "10.0.0.1"
+port = 389
+use_ssl = false
+start_tls = false
+ssl_skip_verify = false
+bind_dn = "cn=admin,dc=grafana,dc=org"
+bind_password = 'grafana'
+search_filter = "(cn=%s)"
+search_base_dns = ["ou=users,dc=grafana,dc=org"]
+
+[servers.attributes]
+name = "givenName"
+surname = "sn"
+username = "cn"
+member_of = "memberOf"
+email =  "email"
+
+[[servers.group_mappings]]
+group_dn = "cn=admins,ou=groups,dc=grafana,dc=org"
+org_role = "Admin"
+grafana_admin = true
+
+# --- Second LDAP Server ---
+
+[[servers]]
+host = "10.0.0.2"
+port = 389
+use_ssl = false
+start_tls = false
+ssl_skip_verify = false
+
+bind_dn = "cn=admin,dc=grafana,dc=org"
+bind_password = 'grafana'
+search_filter = "(cn=%s)"
+search_base_dns = ["ou=users,dc=grafana,dc=org"]
+
+[servers.attributes]
+name = "givenName"
+surname = "sn"
+username = "cn"
+member_of = "memberOf"
+email =  "email"
+
+[[servers.group_mappings]]
+group_dn = "cn=editors,ou=groups,dc=grafana,dc=org"
+org_role = "Editor"
+
+[[servers.group_mappings]]
+group_dn = "*"
+org_role = "Viewer"
+```
+
 ### Active Directory
 
 [Active Directory](https://technet.microsoft.com/en-us/library/hh831484(v=ws.11).aspx) is a directory service which is commonly used in Windows environments.
@@ -247,6 +308,8 @@ email =  "mail"
 # [[servers.group_mappings]] omitted for clarity
 ```
 
+
+
 #### Port requirements
 
 In above example SSL is enabled and an encrypted port have been configured. If your Active Directory don't support SSL please change `enable_ssl = false` and `port = 389`.