allow plugin to inject buttons in the services/invoices widget

[Blesta Addons]

as a developer, we write plugin that do action for services or invoices, it would be useful if the plugin can inject a button or buttons  in the action column, i know this task need some extra work and not simple task, but we though it's a great addition to Blesta.

for what we can use this ?

let say we gave a plugin that is used to allow clients renew a service before the invoice is generated, this option is not available in blesta core, as the only option to renew service from client side it to have the invoice generated by the system,  we prefer if we can inject a new button near to manage button without the need to make a change in core files .

for invoice the same , let say we have a plugin for creating credit note and we need to add a button near to the button actions

i hope the ideas or the intention is clear .