Base harvester broken on 1.6.1

[amercader]

On its current version, ckanext-harvest passed a custom schema to package_create and package_update to allow defining an id for new packages (the same as in remote ckan instances) [1]

Recent changes in the logic layer have made that the context object is no longer directly read from the context, but only get from plugins [2]. This makes the schema sent from ckanext-harvest to be ignored and the harvesting fails because the id field is not expected

ValidationError: {'Id': u'The input field id was not expected.'}

We need a way to either:

1. Be more flexible accepting schemas on the logic functions
2. Modify the harvester plugin to implement the necessary interface

[1] ​https://github.com/okfn/ckanext-harvest/blob/master/ckanext/harvest/harvesters/base.py#L115

[2] ​https://github.com/okfn/ckan/blob/0c07d3be846777318b35c31325215dff00e99313/ckan/logic/action/create.py#L38