chore: Centralize env parsing, validation, defaults, and deprecation notices (#3487)

* chore: Centralize env parsing, defaults, deprecation

* wip

* test

* test

* tsc

* docs, more validation

* fix: Allow empty REDIS_URL (defaults to localhost)

* test

* fix: SLACK_MESSAGE_ACTIONS not bool

* fix: Add SMTP port validation

server/errors.ts

@@ -3,8 +3,7 @@ import env from "./env";
 
 export function AuthenticationError(
   message = "Invalid authentication",
-  // @ts-expect-error ts-migrate(2322) FIXME: Type 'string | undefined' is not assignable to typ... Remove this comment to see the full error message
-  redirectUrl: string = env.URL
+  redirectUrl = env.URL
 ) {
   return httpErrors(401, message, {
     redirectUrl,
@@ -113,8 +112,7 @@ export function MaximumTeamsError(
 
 export function EmailAuthenticationRequiredError(
   message = "User must authenticate with email",
-  // @ts-expect-error ts-migrate(2322) FIXME: Type 'string | undefined' is not assignable to typ... Remove this comment to see the full error message
-  redirectUrl: string = env.URL
+  redirectUrl = env.URL
 ) {
   return httpErrors(400, message, {
     redirectUrl,
@@ -148,8 +146,7 @@ export function OIDCMalformedUserInfoError(
 
 export function AuthenticationProviderDisabledError(
   message = "Authentication method has been disabled by an admin",
-  // @ts-expect-error ts-migrate(2322) FIXME: Type 'string | undefined' is not assignable to typ... Remove this comment to see the full error message
-  redirectUrl: string = env.URL
+  redirectUrl = env.URL
 ) {
   return httpErrors(400, message, {
     redirectUrl,