Fix deleting task relations

While the request body of a DELETE request *can* have data in it, it is not really supported and pretty much undocumented. As such, it doesn't work in all clients and probably broke with recent updates.
This fixes this by moving all parts of the task relation used to identify it in the url.

More Info: https://stackoverflow.com/a/299696/10924593

pkg/swagger/docs.go

@@ -5313,7 +5313,9 @@ var doc = `{
                         }
                     }
                 }
-            },
+            }
+        },
+        "/tasks/{taskID}/relations/{relationKind}/{otherTaskId}": {
             "delete": {
                 "security": [
                     {
@@ -5346,6 +5348,20 @@ var doc = `{
                         "name": "taskID",
                         "in": "path",
                         "required": true
+                    },
+                    {
+                        "type": "string",
+                        "description": "The kind of the relation. See the TaskRelation type for more info.",
+                        "name": "relationKind",
+                        "in": "path",
+                        "required": true
+                    },
+                    {
+                        "type": "integer",
+                        "description": "The id of the other task.",
+                        "name": "otherTaskID",
+                        "in": "path",
+                        "required": true
                     }
                 ],
                 "responses": {

pkg/swagger/swagger.json

@@ -5296,7 +5296,9 @@
                         }
                     }
                 }
-            },
+            }
+        },
+        "/tasks/{taskID}/relations/{relationKind}/{otherTaskId}": {
             "delete": {
                 "security": [
                     {
@@ -5329,6 +5331,20 @@
                         "name": "taskID",
                         "in": "path",
                         "required": true
+                    },
+                    {
+                        "type": "string",
+                        "description": "The kind of the relation. See the TaskRelation type for more info.",
+                        "name": "relationKind",
+                        "in": "path",
+                        "required": true
+                    },
+                    {
+                        "type": "integer",
+                        "description": "The id of the other task.",
+                        "name": "otherTaskID",
+                        "in": "path",
+                        "required": true
                     }
                 ],
                 "responses": {

pkg/swagger/swagger.yaml

@@ -4542,45 +4542,6 @@ paths:
       tags:
       - labels
   /tasks/{taskID}/relations:
-    delete:
-      consumes:
-      - application/json
-      parameters:
-      - description: The relation object
-        in: body
-        name: relation
-        required: true
-        schema:
-          $ref: '#/definitions/models.TaskRelation'
-      - description: Task ID
-        in: path
-        name: taskID
-        required: true
-        type: integer
-      produces:
-      - application/json
-      responses:
-        "200":
-          description: The task relation was successfully deleted.
-          schema:
-            $ref: '#/definitions/models.Message'
-        "400":
-          description: Invalid task relation object provided.
-          schema:
-            $ref: '#/definitions/web.HTTPError'
-        "404":
-          description: The task relation was not found.
-          schema:
-            $ref: '#/definitions/web.HTTPError'
-        "500":
-          description: Internal error
-          schema:
-            $ref: '#/definitions/models.Message'
-      security:
-      - JWTKeyAuth: []
-      summary: Remove a task relation
-      tags:
-      - task
     put:
       consumes:
       - application/json
@@ -4617,6 +4578,56 @@ paths:
       summary: Create a new relation between two tasks
       tags:
       - task
+  /tasks/{taskID}/relations/{relationKind}/{otherTaskId}:
+    delete:
+      consumes:
+      - application/json
+      parameters:
+      - description: The relation object
+        in: body
+        name: relation
+        required: true
+        schema:
+          $ref: '#/definitions/models.TaskRelation'
+      - description: Task ID
+        in: path
+        name: taskID
+        required: true
+        type: integer
+      - description: The kind of the relation. See the TaskRelation type for more info.
+        in: path
+        name: relationKind
+        required: true
+        type: string
+      - description: The id of the other task.
+        in: path
+        name: otherTaskID
+        required: true
+        type: integer
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: The task relation was successfully deleted.
+          schema:
+            $ref: '#/definitions/models.Message'
+        "400":
+          description: Invalid task relation object provided.
+          schema:
+            $ref: '#/definitions/web.HTTPError'
+        "404":
+          description: The task relation was not found.
+          schema:
+            $ref: '#/definitions/web.HTTPError'
+        "500":
+          description: Internal error
+          schema:
+            $ref: '#/definitions/models.Message'
+      security:
+      - JWTKeyAuth: []
+      summary: Remove a task relation
+      tags:
+      - task
   /tasks/all:
     get:
       consumes: