Issue due date (#3794)

* Started adding deadline to ui

* Implemented basic issue due date managing

* Improved UI for due date managing

* Added at least write access to the repo in order to modify issue due dates

* Ui improvements

* Added issue comments creation when adding/modifying/removing a due date

* Show due date in issue list

* Added api support for issue due dates

* Fixed lint suggestions

* Added deadline to sdk

* Updated css

* Added support for adding/modifiying deadlines for pull requests via api

* Fixed comments not created when updating or removing a deadline

* update sdk (will do properly once go-gitea/go-sdk#103 is merged)

* enhanced updateIssueDeadline

* Removed unnessecary Issue.DeadlineString

* UI improvements

* Small improvments to comment creation
+ ui & validation improvements

* Check if an issue is overdue is now a seperate function

* Updated go-sdk with govendor as it was merged

* Simplified isOverdue method

* removed unessecary deadline to 0 set

* Update swagger definitions

* Added missing return

* Added an explanary comment

* Improved updateIssueDeadline method so it'll only update `deadline_unix`

* Small changes and improvements
* no need to explicitly load the issue when updating a deadline, just use whats already there
* small optimisations

* Added check if a deadline was modified before updating it

* Moved comment creating logic into its own function

* Code cleanup for creating deadline comment

* locale improvement

* When modifying a deadline, the old deadline is saved with the comment

* small improvments to xorm session handling when updating an issue deadline
+ style nitpicks

* style nitpicks

* Moved checking for if the user has write acces to middleware

options/locale/locale_en-US.ini

@@ -736,8 +736,22 @@ issues.add_time_minutes = Minutes
 issues.add_time_sum_to_small = No time was entered.
 issues.cancel_tracking = Cancel
 issues.cancel_tracking_history = `cancelled time tracking %s`
+issues.time_spent_total = Total Time Spent
 issues.time_spent_from_all_authors = `Total Time Spent: %s`
-
+issues.due_date = Due date
+issues.invalid_due_date_format = "Due date format is invalid, must be 'yyyy-mm-dd'."
+issues.error_modifying_due_date = "An error occured while modifying the due date."
+issues.error_removing_due_date = "An error occured while remvoing the due date."
+issues.due_date_form = "Due date, format yyyy-mm-dd"
+issues.due_date_form_add = "Add due date"
+issues.due_date_form_update = "Update due date"
+issues.due_date_form_remove = "Remove due date"
+issues.due_date_not_writer = "You need to have at least write access to this repository in order to update the due date for this issue."
+issues.due_date_not_set = "No due date set."
+issues.due_date_added = "added the due date %s %s"
+issues.due_date_modified = "modified the due date to %s from %s %s"
+issues.due_date_remove = "removed the due date %s %s"
+issues.due_date_overdue = "Overdue"
 
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