feat: add an endpoint to manually resume a coder task (#21948)

Closes https://github.com/coder/internal/issues/1262.

This PR adds:
* the `POST /api/experimental/tasks/{user}/{task}/resume` endpoint
* follows conventions from https://github.com/coder/internal/issues/1261
* sets the build reason to `task_resume`
* a task that is not paused (ie. is already running), cannot be resumed.

coderd/apidoc/swagger.json

@@ -5185,6 +5185,44 @@
 				}
 			}
 		},
+		"/tasks/{user}/{task}/resume": {
+			"post": {
+				"security": [
+					{
+						"CoderSessionToken": []
+					}
+				],
+				"consumes": ["application/json"],
+				"tags": ["Tasks"],
+				"summary": "Resume task",
+				"operationId": "resume-task",
+				"parameters": [
+					{
+						"type": "string",
+						"description": "Username, user ID, or 'me' for the authenticated user",
+						"name": "user",
+						"in": "path",
+						"required": true
+					},
+					{
+						"type": "string",
+						"format": "uuid",
+						"description": "Task ID",
+						"name": "task",
+						"in": "path",
+						"required": true
+					}
+				],
+				"responses": {
+					"202": {
+						"description": "Accepted",
+						"schema": {
+							"$ref": "#/definitions/codersdk.ResumeTaskResponse"
+						}
+					}
+				}
+			}
+		},
 		"/tasks/{user}/{task}/send": {
 			"post": {
 				"security": [
@@ -12701,7 +12739,8 @@
 				"ssh_connection",
 				"vscode_connection",
 				"jetbrains_connection",
-				"task_manual_pause"
+				"task_manual_pause",
+				"task_resume"
 			],
 			"x-enum-varnames": [
 				"CreateWorkspaceBuildReasonDashboard",
@@ -12709,7 +12748,8 @@
 				"CreateWorkspaceBuildReasonSSHConnection",
 				"CreateWorkspaceBuildReasonVSCodeConnection",
 				"CreateWorkspaceBuildReasonJetbrainsConnection",
-				"CreateWorkspaceBuildReasonTaskManualPause"
+				"CreateWorkspaceBuildReasonTaskManualPause",
+				"CreateWorkspaceBuildReasonTaskResume"
 			]
 		},
 		"codersdk.CreateWorkspaceBuildRequest": {
@@ -16647,6 +16687,14 @@
 				}
 			}
 		},
+		"codersdk.ResumeTaskResponse": {
+			"type": "object",
+			"properties": {
+				"workspace_build": {
+					"$ref": "#/definitions/codersdk.WorkspaceBuild"
+				}
+			}
+		},
 		"codersdk.RetentionConfig": {
 			"type": "object",
 			"properties": {