Add ability to prevent OIDC redirect (#6544)

* Add ability to prevent OIDC redirect

* Fix Typing on optional boolean

* Fix lint

* Fix lint

* Rename var from PREVENT to DISABLE

---------

Co-authored-by: Tom Moor <tom@getoutline.com>

server/env.ts

@@ -499,6 +499,16 @@ export class Environment {
     process.env.OIDC_USERINFO_URI
   );
 
+  /**
+   * Disable autoredirect to the OIDC login page if there is only one
+   * authentication method and that method is OIDC.
+   */
+  @IsOptional()
+  @IsBoolean()
+  public OIDC_DISABLE_REDIRECT = this.toOptionalBoolean(
+    process.env.OIDC_DISABLE_REDIRECT
+  );
+
   /**
    * The OIDC logout endpoint.
    */
@@ -776,6 +786,26 @@ export class Environment {
       );
     }
   }
+
+  /**
+   * Convert a string to an optional boolean. Supports the following:
+   *
+   * 0 = false
+   * 1 = true
+   * "true" = true
+   * "false" = false
+   * "" = undefined
+   *
+   * @param value The string to convert
+   * @returns A boolean or undefined
+   */
+  private toOptionalBoolean(value: string | undefined) {
+    try {
+      return value ? !!JSON.parse(value) : undefined;
+    } catch (err) {
+      return undefined;
+    }
+  }
 }
 
 const env = new Environment();