Grafana: Evaluate date name (Flux)

Goal: Add two columns (namedMonth and namedDay) with name of the month and day.
Steps:

• Aggregate the data with an window of 1d and the function last.
• Group the data by _time.
• Calculate the sum for each timeseries (foreach grouped _time).
• Truncate the data to whole days.
• Select first to remove the last not completed day.
• Evaluate the month and the day and add these as new columns.