Support Primary Key Metadata

We are trying to get metadata on the Primary Keys using the `QueryServiceMetadata` class `getPrimaryKeys()` method which looks to currently always return an empty list.

```
public ResultSet getPrimaryKeys(String catalog, String schema, String table) throws SQLException {
return new QueryServiceResultSet(Collections.EMPTY_LIST, new QueryServiceResultSetMetaData(QueryServiceDbMetadata.GET_PRIMARY_KEYS));
}
```

From a quick query, we can see that Salesforce does indeed return information about the Primary Keys for each table and looks to be possible to implement.

Example Salesforce Metadata:
```
{
"metadata": [
{
"fields": [
{
"name": "AccountNumber__c",
"displayName": "Account Number",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "AccountSource__c",
"displayName": "Account Source",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "AnnualRevenue__c",
"displayName": "Annual Revenue",
"type": "NUMBER",
"businessType": "NUMBER"
},
{
"name": "BillingCity__c",
"displayName": "Billing City",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "BillingCountry__c",
"displayName": "Billing Country",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "BillingGeocodeAccuracy__c",
"displayName": "Billing Geocode Accuracy",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "BillingLatitude__c",
"displayName": "Billing Latitude",
"type": "NUMBER",
"businessType": "NUMBER"
},
{
"name": "BillingLongitude__c",
"displayName": "Billing Longitude",
"type": "NUMBER",
"businessType": "NUMBER"
},
{
"name": "BillingPostalCode__c",
"displayName": "Billing Zip/Postal Code",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "BillingState__c",
"displayName": "Billing State/Province",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "BillingStreet__c",
"displayName": "Billing Street",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "cdp_sys_SourceVersion__c",
"displayName": "cdp_sys_SourceVersion",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "CreatedById__c",
"displayName": "Created By ID",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "CreatedDate__c",
"displayName": "Created Date",
"type": "DATE_TIME",
"businessType": "DATE_TIME"
},
{
"name": "DataSource__c",
"displayName": "Data Source",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "DataSourceObject__c",
"displayName": "Data Source Object",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "Description__c",
"displayName": "Account Description",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "Fax__c",
"displayName": "Account Fax",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "Id__c",
"displayName": "Account ID",
"type": "STRING",
"keyQualifier": "KQ_Id__c",
"businessType": "TEXT"
},
{
"name": "Industry__c",
"displayName": "Industry",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "IsDeleted__c",
"displayName": "Deleted",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "Jigsaw__c",
"displayName": "Data.com Key",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "JigsawCompanyId__c",
"displayName": "Jigsaw Company ID",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "KQ_Id__c",
"displayName": "KQ_Id",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "LastActivityDate__c",
"displayName": "Last Activity",
"type": "DATE_TIME",
"businessType": "DATE_TIME"
},
{
"name": "LastModifiedById__c",
"displayName": "Last Modified By ID",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "LastModifiedDate__c",
"displayName": "Last Modified Date",
"type": "DATE_TIME",
"businessType": "DATE_TIME"
},
{
"name": "LastReferencedDate__c",
"displayName": "Last Referenced Date",
"type": "DATE_TIME",
"businessType": "DATE_TIME"
},
{
"name": "LastViewedDate__c",
"displayName": "Last Viewed Date",
"type": "DATE_TIME",
"businessType": "DATE_TIME"
},
{
"name": "MasterRecordId__c",
"displayName": "Master Record ID",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "Name__c",
"displayName": "Account Name",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "NumberOfEmployees__c",
"displayName": "Employees",
"type": "NUMBER",
"businessType": "NUMBER"
},
{
"name": "OwnerId__c",
"displayName": "Owner ID",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "ParentId__c",
"displayName": "Parent Account ID",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "Phone__c",
"displayName": "Account Phone",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "PhotoUrl__c",
"displayName": "Photo URL",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "SfdcOrganizationId__c",
"displayName": "SfdcOrganizationId",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "ShippingCity__c",
"displayName": "Shipping City",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "ShippingCountry__c",
"displayName": "Shipping Country",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "ShippingGeocodeAccuracy__c",
"displayName": "Shipping Geocode Accuracy",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "ShippingLatitude__c",
"displayName": "Shipping Latitude",
"type": "NUMBER",
"businessType": "NUMBER"
},
{
"name": "ShippingLongitude__c",
"displayName": "Shipping Longitude",
"type": "NUMBER",
"businessType": "NUMBER"
},
{
"name": "ShippingPostalCode__c",
"displayName": "Shipping Zip/Postal Code",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "ShippingState__c",
"displayName": "Shipping State/Province",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "ShippingStreet__c",
"displayName": "Shipping Street",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "SicDesc__c",
"displayName": "SIC Description",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "SystemModstamp__c",
"displayName": "System Modstamp",
"type": "DATE_TIME",
"businessType": "DATE_TIME"
},
{
"name": "Type__c",
"displayName": "Account Type",
"type": "STRING",
"businessType": "TEXT"
},
{
"name": "Website__c",
"displayName": "Website",
"type": "STRING",
"businessType": "TEXT"
}
],
"category": "Profile",
"name": "Account_Home__dll",
"displayName": "Account_Home",
"primaryKeys": [
{
"name": "Id__c",
"displayName": "Account ID",
"indexOrder": "1"
}
]
}
]
}

```

Is there any plans for the implementation?

Start with QueryServiceMetadata.getPrimaryKeys() and the QueryServiceResultSet and QueryServiceResultSetMetaData classes shown in the issue. Compare the Salesforce metadata response with the JDBC primary-key metadata contract, then add coverage for a table that reports primary-key information. Done means getPrimaryKeys() returns the available primary-key metadata instead of an empty result.

Written by the indexing model from the issue text.