Q: Cannot set function key - sample needed

[Provision Function App](https://azure.microsoft.com/en-us/resources/templates/101-function-app-create-dedicated/)

### Issue Details
Trying to make use of function keys resource according to this https://docs.microsoft.com/en-us/azure/templates/microsoft.web/2018-02-01/sites/functions/keys and getting error:
`New-AzResourceGroupDeployment : 08:09:00 - Error: Code=InvalidRequestContent; Message=The request content was invalid and could not be deserialized: 'Could not find member 'value' on object of type 'TemplateResource'.`

```
{
"apiVersion": "2015-08-01",
"type": "Microsoft.Web/sites",
"name": "[variables('functions_name')]",
"location": "[variables('location')]",
"tags": {
"ccm": "[variables('ccmvalue')]"
},
"kind": "functionapp",
"identity": {
"type": "SystemAssigned"
},
"dependsOn": [
"[variables('appserviceplan_functions_name')]"
],
"properties": {
"serverFarmId": "[resourceId('Microsoft.Web/serverfarms', variables('appserviceplan_functions_name'))]",
"siteConfig": {
"http20Enabled": true
}
},
"resources": [
{
"type": "config",
"apiVersion": "2018-11-01",
"name": "appsettings",
"dependsOn": [
"nestedTemplate",
"[variables('functions_spomanagement_name')]"
],
"properties": {
"APPINSIGHTS_INSTRUMENTATIONKEY": "[reference(resourceId('Microsoft.Insights/components/', variables('appinsights_name')), '2015-05-01').InstrumentationKey]",
"AzureWebJobsStorage": "[concat('@Microsoft.KeyVault(SecretUri=', reference(resourceId(parameters('rg-api-name'), 'Microsoft.KeyVault/vaults/secrets', variables('kv_dss_name'), variables('secrets_storageaccount_connectionstringname')), '2018-02-14').secretUriWithVersion, ')')]",
"FUNCTIONS_EXTENSION_VERSION": "~1",
"FUNCTIONS_WORKER_RUNTIME": "[variables('functions_worker_runtime')]",
"WEBSITE_CONTENTAZUREFILECONNECTIONSTRING": "[concat('@Microsoft.KeyVault(SecretUri=', reference(resourceId(parameters('rg-api-name'),'Microsoft.KeyVault/vaults/secrets', variables('kv_dss_name'), variables('secrets_storageaccount_connectionstringname')), '2018-02-14').secretUriWithVersion, ')')]",
"WEBSITE_CONTENTSHARE": "[toLower(variables('functions_management_name'))]"
}
}
// THIS IS WHAT CAUSES ERROR
//{
// "name": "variables('keys_managementinvocation')",
// "type": "Microsoft.Web/sites/functions/keys",
// "apiVersion": "2018-02-01",
// "value": "[parameters('managementinvocationkey')]"
//}
]
},
```

Start with the linked Provision Function App template and the Microsoft.Web sites/functions/keys reference, then compare the shown nested resource with the documented resource schema. A useful sample should deploy the function key without the InvalidRequestContent deserialization error and make the required resource shape clear.

Written by the indexing model from the issue text.