Fix #248: add `maybe_update_issue_points` step

[leplatrem]

• Requires #247

>>> [f for f in s.client.get_all_fields() if "points" in f["name"].lower()]
[
{'id': 'customfield_10678', 'key': 'customfield_10678', 'name': 'Points Remaining', 'untranslatedName': 'Points Remaining', 'custom': True, 'orderable': True, 'navigable': True, 'searchable': True, 'clauseNames': ['cf[10678]', 'Points Remaining', 'Points Remaining[Number]'], 'schema': {'type': 'number', 'custom': 'com.atlassian.jira.plugin.system.customfieldtypes:float', 'customId': 10678}}, 

{'id': 'customfield_10310', 'key': 'customfield_10310', 'name': 'Original Story Points', 'untranslatedName': 'Original Story Points', 'custom': True, 'orderable': True, 'navigable': True, 'searchable': True, 'clauseNames': ['cf[10310]', 'Original Story Points', 'Original Story Points[Number]'], 'schema': {'type': 'number', 'custom': 'com.atlassian.jira.plugin.system.customfieldtypes:float', 'customId': 10310}}, 

{'id': 'customfield_10037', 'key': 'customfield_10037', 'name': 'Story Points', 'untranslatedName': 'Story Points', 'custom': True, 'orderable': True, 'navigable': True, 'searchable': True, 'clauseNames': ['cf[10037]', 'Story Points', 'Story Points[Number]'], 'schema': {'type': 'number', 'custom': 'com.atlassian.jira.plugin.system.customfieldtypes:float', 'customId': 10037}}]

>>> s.client.update_issue_field(key="FIDEFE-4686", fields={"customfield_10037": 1})
>>>