Introduce helper function to format Ledger CLI output as Org table

This function is ideal, but it's doing the job.  It can be used to
format output of calls to ledger as follows:

    #+begin_src emacs-lisp :results value raw table
    (db/ledger-cli-to-org-table-list
     (concat "ledger -f finance.ledger "
             "--period monthly --depth 2 "
             "--display 'd >= [2024-07-01]' "
             "--empty "
             "lisp ^Expense"))
    #+end_src

site-lisp/db-org.el

@@ -1076,6 +1076,53 @@ _q_ → Quit this hydra"
   ("q" (message "Abort") nil)
   ("C-g" (message "Abort") nil))
 
+(defun db/ledger-cli-to-org-table-list (command)
+  "Run ledger COMMAND and convert the result to Org table list.
+
+COMMAND is expected to be a call to ledger-cli and its `lisp'
+subcommand, the result of which is a list of transactions.  This
+list is converted in such a way that Org can display it as table,
+where the rows are all accounts contained in the result of
+COMMAND, and where the columns are the individual transactions,
+headlined with their date."
+  ;; XXX: this implementation is certainly not ideal
+  (let* ((data (->> command
+                    shell-command-to-string
+                    read-from-string    ; XXX: this needs some error handling
+                    car
+                    ;; Format time and remove unnecessary data
+                    (-map #'(lambda (row)
+                              (list (format-time-string "%F" (nth 2 row))
+                                    (-map #'(lambda (entry)
+                                              (list (nth 1 entry)
+                                                    (nth 2 entry)))
+                                          (-drop 5 row)))))))
+         (months (-map #'-first-item data))
+         funds
+         result)
+
+    (dolist (row data)
+      (let ((month (-first-item row)))
+        (dolist (entry (-second-item row))
+          (let ((fund (-first-item entry))
+                (value (-second-item entry)))
+            (setf (alist-get month (alist-get fund funds nil nil #'string=) nil nil #'string=)
+                  value)))))
+
+    (push (cl-list* "" months) result)
+    (push (cl-list* " " (-repeat (length data) "<r>")) result)
+    (push 'hline result)
+
+    (dolist (fund (-sort #'string< (-map #'-first-item funds)))
+      (push (cl-list* fund
+                      (-map #'(lambda (month)
+                                (alist-get month (alist-get fund funds nil nil #'string=)
+                                           "0.00€" nil #'string=))
+                            months))
+            result))
+
+    (reverse result)))
+
 
 ;;; Checklist Handling