How to create a function to automate header creation?

I have a few transcription to do, using lilypond. It consists of a few songs, all of the same composer/poet, but there might be more to come. I already have a few helper functions in a that I include in each score, but I'd like to have a function to automate header creation, something I could call like this:

\mkheader "my song"

or something similar.

This would avoid the need to write

\header {
  composer = "the composer of all the songs"
  title = "my song"
}

in each song.

Since two days ago, I've been (re-)reading the lilypond documentation, but I can't get it to work. Any ideas?

You are likely needing Include files.

Directory structure:

.
├── my_include.ly
├── my_main.ly

my_include.ly

\header {
  composer = "the composer of all the songs"
  title = "my song"
} 

my_main.ly

\version "2.20.0"

\include "my_include.ly"

melody = \relative c {
  \key c \major
  \time 4/4
  c c c c |
}

\score {
  <<
    \new Staff { \melody }
  >>
}

It might be that you want to add extra information later in your main lilypond file, in which case you just add another header block my_main.ly

\version "2.20.0"

\include "./my_include.ly"

\header {
 subtitle = "my_subtitle"
 subsubtitle = "my_subsubtitle"
}

melody = \relative c'' {
  \key c \major
  \time 4/4
  c c c c |
}

\score {
  <<
    \new Staff { \melody }
  >>
}