Add page localization (#7128)

* added localized pages; added refactored page templates; adapted test cases; introduced localization test cases

* added changelog entry

* fixed test description typo

* fixed bug in PromiseRouter where headers are not added for text reponse

* added page parameters in page headers for programmatic use

* refactored tests for PublicAPIRouter

* added mustache lib for template rendering

* fixed fs.promises module reference

* fixed template placeholder typo

* changed redirect response to provide headers instead of query parameters

* fix lint

* fixed syntax errors and typos in html templates

* removed obsolete URI encoding

* added locale inferring from request body and header

* added end-to-end localizaton test

* added server option validation; refactored pages server option

* fixed invalid redirect URL for no locale matching file

* added end-to-end localizaton tests

* adapted tests to new response content

* re-added PublicAPIRouter; added PagesRouter as experimental feature

* refactored PagesRouter test structure

* added configuration option for custom path to pages

* added configuration option for custom endpoint to pages

* fixed lint

* added tests

* added a distinct page for invalid password reset link

* renamed generic page invalidLink to expiredVerificationLink

* improved HTML files documentation

* improved HTML files documentation

* changed changelog entry for experimental feature

* improved file naming to make it more descriptive

* fixed file naming and env parameter naming

* added readme entry

* fixed readme TOC - hasn't been updated in a while

* added localization with JSON resource

* added JSON localization to feature pages (password reset, email verification)

* updated readme

* updated readme

* optimized JSON localization for feature pages; added e2e test case

* fixed readme typo

* minor refactoring of existing tests

* fixed bug where Object type was not recognized as config key type

* added feature config placeholders

* prettier

* added passing locale to page config placeholder callback

* refactored passing locale to placeholder to pass test

* added config placeholder feature to README

* fixed typo in README

package.json

@@ -47,6 +47,7 @@
     "lru-cache": "5.1.1",
     "mime": "2.5.0",
     "mongodb": "3.6.3",
+    "mustache": "4.1.0",
     "parse": "2.19.0",
     "pg-promise": "10.9.1",
     "pluralize": "8.0.0",