🔄🔐 refactor: auth; style: match OpenAI; feat: custom social login order (#1421)

* refactor(Login & Registration)

* fix(Registration) test errors

* refactor(LoginForm & ResetPassword)

* fix(LoginForm): display 'undefined' when loading page; style(SocialButton): match OpenAI's graphics

* some refactor and style update for social logins

* style: width like OpenAI; feat: custom social login order; refactor: alphabetical socials

* fix(Registration & Login) test

* Update .env.example

* Update .env.example

* Update dotenv.md

* refactor: remove `SOCIAL_LOGIN_ORDER` for `socialLogins` configured from `librechat.yaml`
- initialized by AppService, attached as app.locals property
- rename socialLoginOrder and loginOrder to socialLogins app-wide for consistency
- update types and docs
- initialize config variable as array and not singular string to parse
- bump data-provider to 0.3.9

---------

Co-authored-by: Danny Avila <messagedaniel@protonmail.com>

docs/install/configuration/custom_config.md

@@ -31,6 +31,7 @@ Stay tuned for ongoing enhancements to customize your LibreChat instance!
     - [Registration](#registration)
     - [Endpoints](#endpoints)
   - [Registration Object Structure](#registration-object-structure)
+    - [**socialLogins**:](#socialLogins)
     - [**allowedDomains**:](#allowedDomains)
   - [Custom Endpoint Object Structure](#custom-endpoint-object-structure)
     - [**name**:](#name)
@@ -112,6 +113,9 @@ docker-compose up # no need to rebuild
 - **Key**: `registration`
 - **Type**: Object
 - **Description**: Configures registration-related settings for the application.
+  - **Sub-Key**: `socialLogins`
+  - **Type**: Array of Strings (`"google"`, `"facebook"`, `"openid"`, `"github"`, `"discord"`)
+  - **Description**: Determines both the available social login providers and their arranged order to list on the login/registration page, from top to bottom (first to last values). Note: a login option will not appear even if listed if not [properly configured.](./user_auth_system.md#social-authentication-setup-and-configuration)
   - **Sub-Key**: `allowedDomains`
   - **Type**: Array of Strings
   - **Description**: Specifies a list of allowed email domains for user registration. Users attempting to register with email domains not listed here will be restricted from registering.
@@ -132,11 +136,23 @@ docker-compose up # no need to rebuild
 ```yaml
 # Example Registration Object Structure
 registration:
+  socialLogins: ["google", "facebook", "github", "discord", "openid"]
   allowedDomains:
     - "gmail.com"
     - "protonmail.com"
 ```
 
+### **socialLogins**:
+
+  > Defines the available social login providers and their display order.
+
+  - Type: Array of Strings
+  - Example: 
+    ```yaml
+    socialLogins: ["google", "facebook", "github", "discord", "openid"]
+    ```
+  - **Note**: The order of the providers in the list determines their appearance order on the login/registration page. Each provider listed must be [properly configured](./user_auth_system.md#social-authentication-setup-and-configuration) within the system to be active and available for users. This configuration allows for a tailored authentication experience, emphasizing the most relevant or preferred social login options for your user base.
+
 ### **allowedDomains**:
 
   > A list specifying allowed email domains for registration.

docs/install/configuration/dotenv.md

@@ -666,7 +666,6 @@ see: **[User/Auth System](../configuration/user_auth_system.md)**
 ```bash
 ALLOW_EMAIL_LOGIN=true
 ALLOW_REGISTRATION=true
-ALLOWED_REGISTRATION_DOMAINS=
 ALLOW_SOCIAL_LOGIN=false
 ALLOW_SOCIAL_REGISTRATION=false
 ```