SqlRS: Add support for SQL credentials for Reporting Services DB init

xSQLServerRSConfig resource currently does not support DB initialisation using SQL auth. This is needed in a scenario when deploying RS DBs to a remote SQL server in a non-domain environment.

Suggested .mof schema change:

[ClassVersion("1.0.0.0"), FriendlyName("xSQLServerRSConfig")]
class MSFT_xSQLServerRSConfig : OMI_BaseResource
{
       [Key, Description("Name of the SQL Server Reporting Services instance to be configured.")] String InstanceName;
       [Required, Description("Name of the SQL Server to host the Reporting Service database.")] String RSSQLServer;
       [Required, Description("Name of the SQL Server instance to host the Reporting Service database.")] String RSSQLInstanceName;
==>    [Write, EmbeddedInstance("MSFT_Credential"), Description("SQL authentication credential to be used for DB initialisation.")] String RSSQLCredential;
       [Read, Description("Is the Reporting Services instance initialized.")] Boolean IsInitialized;
};

Details of the scenario you tried and the problem that is occurring:

The DSC configuration that is using the resource (as detailed as possible):

Version of the Operating System, SQL Server and PowerShell the DSC Target Node is running:

What module (SqlServer or SQLPS) and which version of the module the DSC Target Node is running:

Version of the DSC module you're using, or 'dev' if you're using current dev branch:

Start by locating the xSQLServerRSConfig resource and its MOF schema. Review how Reporting Services database initialization currently receives server and instance settings, then trace the path used for remote, non-domain SQL Server deployments. Done means the resource schema accepts an SQL authentication credential and database initialization supports that scenario.