SHA parameter in accept merge request API

Request by a customer:

[..] You could solve this problem for us by adding an optional SHA parameter to the accept merge request endpoint. GitHub has that which makes accepting merge requests programmatically much safer [...]

This means that to accept a MR through the API, you give a sha parameter which has to match the HEAD of the MR.

This helps preventing race conditions or merging anything you didn't intend to merge when using the API.