Ultimate Member - Social Login 2.5.6

* Added: New function that changes the "Sign in" text to "Sign up" when Social buttons are enabled in an Ultimate Member Register page.
* Tweaked: Twitter button has been changed to the new `X` logo with black background & white text colors.
* Fixed: Error notices with Facebook authentication.
* Fixed: Typo error in `um_social_do_login_error` action hook parameters.
* Fixed: Closes overlay when submitting Register form with required fields.
* Fixed: Case when extension isn't active based on dependency, but we can provide the license key field
* Tweaked: Implementation of wp_safe_redirect(). If you're redirecting users to another host/domain, please add them to the allowed redirect hosts using the filter hook: allowed_redirect_hosts | Hook | WordPress Developer Resources

* IMPORTANT: Breaking Changes
- This new version requires Ultimate Member version 2.6.11+
- Deprecated: Some methods have been renamed/changed to improve and completely comply to PHP & WordPress Coding Standards.
If you have made customizations with Social Login class methods or functions that have variable names in CamelCases, please update them in your customization and use lowercase letters and separate words via underscores.
Examples:
- `getConnectURL()` to `get_connect_url()`
- `getDisconnectURL()` to `get_disconnect_url()`
- `getCallbackURL()` to `get_callback_url()`
- New: LinkedIn API is now offering a way for your app to authenticate members using OpenID Connect. The old LinkedIn API for Login has been deprecated. With this update, the feature "Sign In with LinkedIn using OpenID Connect" should be enabled in your LinkedIn App settings under the Product tab. To use the old LinkedIn API connection(3-legged OAuth Flow), please use the code snippet in the link: Social Login: LinkedIn App Setup - Ultimate Member
* Fixed: Wrong Register forms & fields displayed on Social Overlay.
* Fixed: APIs request errors in the background process & error logs.
* Added: Notice for success and error messages when Social Account has been linked or already in used by other users using Social Shortcode.

* Fixed: PHP warnings
* Fixed: Showing Social Login buttons with Shortcode
* Fixed: Fatal error with Sessions.