Enhance Add-SPServerScaleOutDatabase documentation

Added DatabaseServerCertificateHostName parameter to Add-SPServerScaleOutDatabase cmdlet documentation, specifying its purpose and requirements.

Author: stefangossner

sharepoint/sharepoint-server-ps/SharePointServer/Add-SPServerScaleOutDatabase.md

@@ -18,7 +18,7 @@ Adds an existing scale-out content database to the specified service application
 ```
 Add-SPServerScaleOutDatabase -DatabaseName <String> -ServiceApplication <SPServiceApplicationPipeBind>
  [-AssignmentCollection <SPAssignmentCollection>] [-Confirm] [-DatabaseCredentials <PSCredential>]
- [-DatabaseFailoverServer <String>] [-DatabaseServer <String>] [-WhatIf] [-DeferUpgradeActions]
+ [-DatabaseFailoverServer <String>] [-DatabaseServer <String>] [-WhatIf] [-DeferUpgradeActions] [-DatabaseServerCertificateHostName <String>] 
  [<CommonParameters>]
 ```
 
@@ -209,6 +209,24 @@ Accept pipeline input: False
 Accept wildcard characters: False
 ```
 
+### DatabaseServerCertificateHostName 
+
+> Applicable: SharePoint Server Subscription Edition
+
+Specifies the host name that is used to validate the SQL Server TLS certificate when establishing the database connection.
+
+```yaml
+Type: String
+Parameter Sets: (All)
+Aliases:
+
+Required: True
+Position: Named
+Default value: None
+Accept pipeline input: False
+Accept wildcard characters: False
+```
+
 ### CommonParameters
 This cmdlet supports the common parameters: -Debug, -ErrorAction, -ErrorVariable, -InformationAction, -InformationVariable, -OutVariable, -OutBuffer, -PipelineVariable, -Verbose, -WarningAction, and -WarningVariable. For more information, see about_CommonParameters (https://go.microsoft.com/fwlink/?LinkID=113216).