The order of how owners of XML nodes are executed feels more or less like a mystery, and can lead to unexpected results:
Latest examples are:
* T5863
* T5852
As discussed during the maintainer meeting we should make the XML `<priority>` node mandatory if the parent node has an owner.
## Example
### Invalid
```
<node name="dynamic" owner="${vyos_conf_scripts_dir}/dns_dynamic.py">
<properties>
<help>Dynamic DNS</help>
</properties>
<children>
...
</children>
</node>
```
### Valid
```
<node name="dynamic" owner="${vyos_conf_scripts_dir}/dns_dynamic.py">
<properties>
<help>Dynamic DNS</help>
<priority>990</priority>
</properties>
<children>
...
</children>
</node>
```