Task: Review `WordPressExternalConnection::push()` altered return type

[helen]

At some or various points during the development of the next release, we need to follow up on #630 which changes the return type of {ConnectionType}::push(). We will likely need some combination of the following:

• Developer communication about the change (proactive as well as passive documentation)
• A review of the return type on concert with similar/parallel functions
• Potential mitigation of effects on third-party integrations