Python-redmine

- Added: WikiPage resource now automatically requests all of it's available attributes from Redmine in case if some of them are not available in an existent resource object
- Added: Support for setting date/datetime resource attributes using date/datetime Python objects
- Added: Support for using date/datetime Python objects in all ResourceManager methods, i.e. `new()`, `create()`, `update()`, `delete()`, `get()`, `all()`, `filter()`
- Fixed: Issue 14 (Python Redmine was incorrectly raising `ResourceAttrError` when trying to call `repr()`, `str()` and `int()` on resources, created via `new()` method

- Fixed: Project resource `status` attribute was converted to IssueStatus resource by mistake

- Fixed: Issue 10 (Python Redmine was incorrectly raising `ResourceAttrError` while creating some resources via `new()` method)

- Added: `Redmine.auth()` shortcut for the case if we just want to check if user provided
valid auth credentials, can be used for user authentication on external resource based on
Redmine user database (see [docs](https://python-redmine.com/advanced/external_auth.html) for details)
- Fixed: `JSONDecodeError` was raised in some Redmine versions during some create/update
operations (thanks to [0x55aa](https://github.com/0x55aa))
- Fixed: User resource `status` attribute was converted to IssueStatus resource by mistake

- Added: An ability to create custom resources which allow to easily redefine the behaviour
of existing resources (see docs for details)
- Added: An ability to add/remove watcher to/from issue (see docs for details)
- Added: An ability to add/remove users to/from group (see docs for details)

- Added: New exceptions:
- ConflictError
- ReadonlyAttrError
- ResultSetTotalCountError
- CustomFieldValueError
- Added: Update functionality via `update()` and `save()` methods for resources (see docs for details):
- User
- Group
- IssueCategory
- Version
- TimeEntry
- ProjectMembership
- WikiPage
- Project
- Issue
- Added: Limit/offset support via `all()` and `filter()` methods for resources that
doesn't support that feature via Redmine:
- IssueRelation
- Version
- WikiPage
- IssueStatus
- Tracker
- Enumeration
- IssueCategory
- Role
- Group
- CustomField
- Added: On demand includes, e.g. in addition to `redmine.group.get(1, include='users')` users for a group can also be retrieved on demand via `group.users` if include wasn't set (see each resource docs for details)
- Added: `total_count` attribute to ResourceSet object which holds the total number of resources for the current resource type available in Redmine (thanks to [Andrei Avram](https://github.com/andreiavram))
- Added: An ability to return `None` instead of raising a `ResourceAttrError` for all or selected resource objects via `raise_attr_exception` kwarg on Redmine object (see docs for details or Issue 6)
- Added: `pre_create()`, `post_create()`, `pre_update()`, `post_update()` resource object methods which can be used to execute tasks that should be done before/after creating/updating the resource through `save()` method
- Added: Allow to create resources in alternative way via `new()` method (see docs for details)
- Added: Allow daterange TimeEntry resource filtering via `from_date` and `to_date` keyword arguments (thanks to [Antoni Aloy](https://github.com/aaloy))
- Added: An ability to retrieve Issue version via `version` attribute in addition to
`fixed_version` to be more obvious
- Changed: Documentation for resources rewritten from scratch to be more understandable
- Fixed: Saving custom fields to Redmine didn't work in some situations
- Fixed: Issue's `fixed_version` attribute was retrieved as dict instead of Version resource object
- Fixed: Resource relations were requested from Redmine every time instead of caching the result after first request
- Fixed: Issue 2 (limit/offset as keyword arguments were broken)
- Fixed: Issue 5 (Version resource `status` attribute was converted to IssueStatus resource by mistake) (thanks to [Andrei Avram](https://github.com/andreiavram))
- Fixed: A lot of small fixes, enhancements and refactoring here and there