Why this change?
Previously just using the `addToolbarPopupMenuOptionsCallback` plugin
API itself was insufficient because it required the return object to
include an `action` key which only accepted a name of the action
function as a string. This was highly problematic because the action
function had to be defined on the `composer` service which means using
the `modifyClass` API to add the action function. This made the API
awkward to use leading to poor developer experiencec.
What does this change do?
This commit introduces a couple of improvemnts to the API.
1. First the API has been renamed to `addComposerToolbarPopupMenuOption` because
the API no longer accepts a callback function which was quite
redundant. Instead, it now accepts an Object. The
`addToolbarPopupMenuOptionsCallback` API function is deprecated and
will be dropped in Discourse 3.3. Note that passing the API a
function is still supported but will be dropped when the `addToolbarPopupMenuOptionsCallback`
is removed.
2. The `action` key in the Object passed to the function can now be a
function and is passed the `toolbarEvent` object when called.
3. The `condition` on key in the Object passed to the function can now be a
function and is passed the `composer` service when called.
