How to split org-roam-capture-templates in to multiple lines?

Question

I have following config for my org-roam:

(use-package org-roam
  :ensure t
  :init
  (setq org-roam-v2-ack t)
  :custom
  (org-roam-directory "~/roamnotes")
  (org-roam-completion-everywhere t)
(org-roam-capture-templates
   '(("d" "Default" plain
      "%?"
      :if-new (file+head
               "%<%Y%m%d%H%M%S>-${slug}.org" 
               "#+title: ${title}\n#+filetags: :nohtmlexport:\n#+date: %U\n#+auto_tangle: nil") ;; I want to split this long line
      :unnarrowed t)
     ))
  :config
  (org-roam-setup)
  (require 'org-roam-dailies)
  (org-roam-db-autosync-mode)
  )

What I want to do: To split long line: "#+title: ${title}\n#+filetags: :nohtmlexport:\n#+date: %U\n#+auto_tangle: nil".

---

What I've tried so far I: This works without an error, but stylistically looks very bad. (Just bad indent)

  ...
  ...
  (org-roam-capture-templates
   '(("d" "Default" plain
      "%?"
      :if-new (file+head
               "%<%Y%m%d%H%M%S>-${slug}.org"
               "#+title: ${title}
#+filetags: :nohtmlexport:
#+date: %U
#+auto_tangle: nil")
      :unnarrowed t)
     ))
  ...
  ...
  )

What I've tried so far II: This stylistically desirable, but this gets an error:

  (org-roam-capture-templates
   '(("d" "Default" plain
      "%?"
      :if-new (file+head
               "%<%Y%m%d%H%M%S>-${slug}.org"
               (concat
                "#+title: ${title}\n"
                "#+filetags: :nohtmlexport:\n"
                "#+date: %U\n"
                "#+auto_tangle: nil"
                )
               )
      :unnarrowed t)
     ))

org-roam-capture--fill-template: Wrong type argument: char-or-string-p, (concat "#+title: ${title}
" "#+filetags: :nohtmlexport:
" "#+date: %U
" "#+auto_tangle: nil")

---

Question:

• Why I can't use concat inside org-roam-capture-templates as written in above?
• If it's possible to use concat (or anything else), how to implement it?