Rely on emacsql-sqlite-open to pick the best available back-end

That function was added two years ago and the first release that
provided it was v4.0.0.  It automatically picks the best available
back-end, `emacsql-sqlite-builtin' or `emacsql-sqlite-module'.
In v4.0.0 it could also fall back to the legacy `emacsql-sqlite'.
The inferior third-party back-ends are no longer supported.

Emacsql v4.1.0, which will be releases in early December, removes
the legacy `emacsql-sqlite' back-end (which used a custom binary).

org-roam-db.el

@@ -36,40 +36,6 @@
 (defvar org-outline-path-cache)
 
 ;;; Options
-(defcustom org-roam-database-connector (if (and (progn
-                                                  (require 'emacsql-sqlite-builtin nil t)
-                                                  (functionp 'emacsql-sqlite-builtin))
-                                                (functionp 'sqlite-open))
-                                           'sqlite-builtin
-                                         'sqlite-module)
-  "The database connector used by Org-roam.
-This must be set before `org-roam' is loaded.  To use an alternative
-connector you must install the respective package explicitly.
-If you are using Emacs 29 or newer, then the default connector is
-`sqlite-builtin', which uses the new builtin support for SQLite.
-You need to install the `emacsql-sqlite-builtin' package to use
-this connector.
-If you are using an older Emacs release, then the default
-connector is `sqlite-module', which uses the module provided by
-the `sqlite3' package.  This is very similar to the previous
-connector and the built-in support in Emacs 29 derives from this
-module.  You need to install the `emacsql-sqlite-module' package
-to use this connector.
-For the time being `libsqlite3' is still supported.  Do not use
-this, it is an older version of the `sqlite-module' connector
-from before the connector and the package were renamed.
-For the time being `sqlite3' is also supported.  Do not use this.
-This uses the third-party `emacsql-sqlite3' package, which uses
-the official `sqlite3' cli tool, which is not intended
-to be used like this.  See https://nullprogram.com/blog/2014/02/06/."
-  :package-version '(forge . "0.3.0")
-  :group 'org-roam
-  :type '(choice
-          (const sqlite-builtin)
-          (const sqlite-module)
-          (const :tag "libsqlite3 (OBSOLETE)" libsqlite3)
-          (const :tag "sqlite3 (BROKEN)" sqlite3)))
-
 (defcustom org-roam-db-location (locate-user-emacs-file "org-roam.db")
   "The path to file where the Org-roam database is stored.
 
@@ -153,31 +119,6 @@ ROAM_REFS."
   (gethash (expand-file-name (file-name-as-directory org-roam-directory))
            org-roam-db--connection))
 
-(declare-function emacsql-sqlite3 "ext:emacsql-sqlite3")
-(declare-function emacsql-libsqlite3 "ext:emacsql-libsqlite3")
-(declare-function emacsql-sqlite-builtin "ext:emacsql-sqlite-builtin")
-(declare-function emacsql-sqlite-module "ext:emacsql-sqlite-module")
-
-(defun org-roam-db--conn-fn ()
-  "Return the function for creating the database connection."
-  (cl-case org-roam-database-connector
-    (sqlite-builtin
-     (progn
-       (require 'emacsql-sqlite-builtin)
-       #'emacsql-sqlite-builtin))
-    (sqlite-module
-     (progn
-       (require 'emacsql-sqlite-module)
-       #'emacsql-sqlite-module))
-    (libsqlite3
-     (progn
-       (require 'emacsql-libsqlite3)
-       #'emacsql-libsqlite3))
-    (sqlite3
-     (progn
-       (require 'emacsql-sqlite3)
-       #'emacsql-sqlite3))))
-
 (defun org-roam-db ()
   "Entrypoint to the Org-roam sqlite database.
 Initializes and stores the database, and the database connection.
@@ -186,11 +127,8 @@ Performs a database upgrade when required."
                (emacsql-live-p (org-roam-db--get-connection)))
     (let ((init-db (not (file-exists-p org-roam-db-location))))
       (make-directory (file-name-directory org-roam-db-location) t)
-      (let ((conn (funcall (org-roam-db--conn-fn) org-roam-db-location)))
+      (let ((conn (emacsql-sqlite-open org-roam-db-location)))
         (emacsql conn [:pragma (= foreign_keys ON)])
-        (when-let* ((process (emacsql-process conn))
-                    (_ (processp process)))
-          (set-process-query-on-exit-flag process nil))
         (puthash (expand-file-name (file-name-as-directory org-roam-directory))
                  conn
                  org-roam-db--connection)