Currently, we do not restrict meta-attributes to those that Pacemaker supports, but allow users to specify custom names. These can be used by user tooling, or in location constraint rules (using value-source set to meta in a node expression). This is flexible but makes it easy to make mistakes such as misspelling a meta-attribute name.

We should offer a distinct syntax for these (maybe custom?), allow that to be used as a value-source, and deprecate support for custom meta-attributes. For example:

<primitive id="rsc1" ...>
  <meta_attributes .../>
  <instance_attributes .../>
  <custom>
     <nvpair id="custom1" name="department" value="accounting"/>
  </custom>
</primitive>
...
<expression ... attribute="department" value="accounting" value-source="custom"/>