# Group Categories

## Linked Properties
|  Link           | Description                                         | Type          | Constraints | Supported operations |
|:---------------:| --------------------------------------------------- | ------------- | ----------- | -------------------- |
| self            | This category                                       | Category      | not null    | READ                 |
| project         | The project of this category                        | Project       | not null    | READ                 |
| defaultAssignee | Default assignee for work packages of this category | User          |             | READ                 |

## Local Properties
| Property   | Description   | Type    | Constraints | Supported operations |
| :--------: | ------------- | ------- | ----------- | -------------------- |
| id         | Category id   | Integer | x > 0       | READ                 |
| name       | Category name | String  |             | READ                 |

## Categories by Project [/api/v3/projects/{project_id}/categories]

+ Model
    + Body

            {
                "_links": {
                    "self": { "href": "/api/v3/projects/11/categories" }
                },
                "total": 2,
                "count": 2,
                "_type": "Collection",
                "_embedded":
                {
                    "elements": [
                        {
                            "_links": {
                                "self": {
                                    "href": "/api/v3/categories/10",
                                    "title": "Category with assignee"
                                },
                                "project": {
                                    "href": "/api/v3/projects/11",
                                    "title": "Example project"
                                },
                                "defaultAssignee": {
                                    "href": "/api/v3/users/42",
                                    "title": "John Sheppard"
                                }
                            },
                            "_type": "Category",
                            "id": 10,
                            "name": "Foo"
                        },
                        {
                            "_links": {
                                "self": { "href": "/api/v3/categories/11" },
                                "project": { "href": "/api/v3/projects/11" }
                            },
                            "_type": "Category",
                            "id": 11,
                            "name": "Bar"
                        }
                    ]
                }
            }

## List categories of a project [GET]

+ Parameters
    + project_id (required, integer, `1`) ... ID of the project whoose categories will be listed

+ Response 200 (application/hal+json)

    [Categories by Project][]

+ Response 404 (application/hal+json)

    Returned if the project does not exist or the client does not have sufficient permissions
    to see it.

    **Required permission:** view project

    *Note: A client without sufficient permissions shall not be able to test for the existence of a project.
    That's why a 404 is returned here, even if a 403 might be more appropriate.*

    + Body

            {
                "_type": "Error",
                "errorIdentifier": "urn:openproject-org:api:v3:errors:NotFound",
                "message": "The specified project does not exist."
            }

## Category [/api/v3/categories/{id}]

+ Model
    + Body

            {
                "_links": {
                    "self": {
                        "href": "/api/v3/categories/10",
                        "title": "Category with assignee"
                     },
                    "project": {
                        "href": "/api/v3/projects/11",
                        "title": "Example project"
                    },
                    "defaultAssignee": {
                        "href": "/api/v3/users/42",
                        "title": "John Sheppard"
                    }
                },
                "_type": "Category",
                "id": 10,
                "name": "Foo"
            }

## View Category [GET]

+ Parameters
    + id (required, integer, `1`) ... category id

+ Response 200 (application/hal+json)

    [Category][]

+ Response 404 (application/hal+json)

    Returned if the category does not exist or the client does not have sufficient permissions
    to see it.

    **Required permission:** view project (defining the category)

    *Note: A client without sufficient permissions shall not be able to test for the existence of
    a category. That's why a 404 is returned here, even if a 403 might be more appropriate.*

    + Body

            {
                "_type": "Error",
                "errorIdentifier": "urn:openproject-org:api:v3:errors:NotFound",
                "message": "The specified category does not exist."
            }