Implement Task API methods (CRUD operations)

- GetTask: retrieve single task by ID
- GetAllTasks: retrieve all tasks for a project with status filter
- CreateTask: create new task and return the created task
- UpdateTask: partial updates via pointer fields
- CloseTask/OpenTask: status operations with proper error handling
- Returns ErrTaskNotFound, ErrTaskClosed, ErrTaskOpen as appropriate
- Comprehensive test coverage for all methods and edge cases

tasks.go

@@ -0,0 +1,102 @@
+package kanboard
+
+import (
+	"context"
+	"fmt"
+)
+
+// GetTask returns a task by its ID.
+// Returns ErrTaskNotFound if the task does not exist.
+func (c *Client) GetTask(ctx context.Context, taskID int) (*Task, error) {
+	params := map[string]int{"task_id": taskID}
+
+	var result *Task
+	if err := c.call(ctx, "getTask", params, &result); err != nil {
+		return nil, fmt.Errorf("getTask: %w", err)
+	}
+
+	if result == nil {
+		return nil, fmt.Errorf("%w: task %d", ErrTaskNotFound, taskID)
+	}
+
+	return result, nil
+}
+
+// GetAllTasks returns all tasks for a project with the specified status.
+func (c *Client) GetAllTasks(ctx context.Context, projectID int, status TaskStatus) ([]Task, error) {
+	params := map[string]int{
+		"project_id": projectID,
+		"status_id":  int(status),
+	}
+
+	var result []Task
+	if err := c.call(ctx, "getAllTasks", params, &result); err != nil {
+		return nil, fmt.Errorf("getAllTasks: %w", err)
+	}
+
+	return result, nil
+}
+
+// CreateTask creates a new task and returns the created task.
+func (c *Client) CreateTask(ctx context.Context, req CreateTaskRequest) (*Task, error) {
+	var taskID int
+	if err := c.call(ctx, "createTask", req, &taskID); err != nil {
+		return nil, fmt.Errorf("createTask: %w", err)
+	}
+
+	if taskID == 0 {
+		return nil, fmt.Errorf("createTask: failed to create task")
+	}
+
+	// Fetch the created task to return full details
+	return c.GetTask(ctx, taskID)
+}
+
+// UpdateTask updates an existing task.
+// Only non-nil fields in the request will be updated.
+func (c *Client) UpdateTask(ctx context.Context, req UpdateTaskRequest) error {
+	var success bool
+	if err := c.call(ctx, "updateTask", req, &success); err != nil {
+		return fmt.Errorf("updateTask: %w", err)
+	}
+
+	if !success {
+		return fmt.Errorf("updateTask: update failed")
+	}
+
+	return nil
+}
+
+// CloseTask closes a task (sets it to inactive).
+// Returns ErrTaskClosed if the task is already closed.
+func (c *Client) CloseTask(ctx context.Context, taskID int) error {
+	params := map[string]int{"task_id": taskID}
+
+	var success bool
+	if err := c.call(ctx, "closeTask", params, &success); err != nil {
+		return fmt.Errorf("closeTask: %w", err)
+	}
+
+	if !success {
+		return fmt.Errorf("%w: task %d", ErrTaskClosed, taskID)
+	}
+
+	return nil
+}
+
+// OpenTask opens a task (sets it to active).
+// Returns ErrTaskOpen if the task is already open.
+func (c *Client) OpenTask(ctx context.Context, taskID int) error {
+	params := map[string]int{"task_id": taskID}
+
+	var success bool
+	if err := c.call(ctx, "openTask", params, &success); err != nil {
+		return fmt.Errorf("openTask: %w", err)
+	}
+
+	if !success {
+		return fmt.Errorf("%w: task %d", ErrTaskOpen, taskID)
+	}
+
+	return nil
+}