public_url_file in .env causes server start error (#15898)

* allow *_FILE environment vars to overwrite default values

* added test

* added mock for fs

* removed test

api/src/env.test.ts

@@ -19,6 +19,7 @@ describe('env processed values', () => {
 
 	afterEach(() => {
 		process.env = originalEnv;
+		jest.resetAllMocks();
 	});
 
 	test('Number value should be a number', () => {

api/src/env.ts

@@ -401,7 +401,7 @@ function processValues(env: Record<string, any>) {
 		if (key.length > 5 && key.endsWith('_FILE')) {
 			newKey = key.slice(0, -5);
 			if (allowedEnvironmentVars.some((pattern) => pattern.test(newKey as string))) {
-				if (newKey in env) {
+				if (newKey in env && !(newKey in defaults && env[newKey] === defaults[newKey])) {
 					throw new Error(
 						`Duplicate environment variable encountered: you can't use "${newKey}" and "${key}" simultaneously.`
 					);