Implement Comment API methods

- GetAllComments: retrieve all comments for a task
- GetComment: retrieve single comment by ID
- CreateComment: create comment and return the created comment
- UpdateComment: update comment content
- RemoveComment: delete a comment
- TaskScope.GetComments and AddComment for fluent API
- Returns ErrCommentNotFound when appropriate
- Comprehensive test coverage

comments.go

@@ -0,0 +1,91 @@
+package kanboard
+
+import (
+	"context"
+	"fmt"
+)
+
+// GetAllComments returns all comments for a task.
+func (c *Client) GetAllComments(ctx context.Context, taskID int) ([]Comment, error) {
+	params := map[string]int{"task_id": taskID}
+
+	var result []Comment
+	if err := c.call(ctx, "getAllComments", params, &result); err != nil {
+		return nil, fmt.Errorf("getAllComments: %w", err)
+	}
+
+	return result, nil
+}
+
+// GetComment returns a comment by its ID.
+// Returns ErrCommentNotFound if the comment does not exist.
+func (c *Client) GetComment(ctx context.Context, commentID int) (*Comment, error) {
+	params := map[string]int{"comment_id": commentID}
+
+	var result *Comment
+	if err := c.call(ctx, "getComment", params, &result); err != nil {
+		return nil, fmt.Errorf("getComment: %w", err)
+	}
+
+	if result == nil {
+		return nil, fmt.Errorf("%w: comment %d", ErrCommentNotFound, commentID)
+	}
+
+	return result, nil
+}
+
+// CreateComment creates a new comment on a task and returns the created comment.
+func (c *Client) CreateComment(ctx context.Context, taskID, userID int, content string) (*Comment, error) {
+	params := map[string]any{
+		"task_id": taskID,
+		"user_id": userID,
+		"content": content,
+	}
+
+	var commentID int
+	if err := c.call(ctx, "createComment", params, &commentID); err != nil {
+		return nil, fmt.Errorf("createComment: %w", err)
+	}
+
+	if commentID == 0 {
+		return nil, fmt.Errorf("createComment: failed to create comment")
+	}
+
+	// Fetch the created comment to return full details
+	return c.GetComment(ctx, commentID)
+}
+
+// UpdateComment updates the content of a comment.
+func (c *Client) UpdateComment(ctx context.Context, commentID int, content string) error {
+	params := map[string]any{
+		"id":      commentID,
+		"content": content,
+	}
+
+	var success bool
+	if err := c.call(ctx, "updateComment", params, &success); err != nil {
+		return fmt.Errorf("updateComment: %w", err)
+	}
+
+	if !success {
+		return fmt.Errorf("updateComment: update failed")
+	}
+
+	return nil
+}
+
+// RemoveComment deletes a comment.
+func (c *Client) RemoveComment(ctx context.Context, commentID int) error {
+	params := map[string]int{"comment_id": commentID}
+
+	var success bool
+	if err := c.call(ctx, "removeComment", params, &success); err != nil {
+		return fmt.Errorf("removeComment: %w", err)
+	}
+
+	if !success {
+		return fmt.Errorf("removeComment: delete failed")
+	}
+
+	return nil
+}