feat: Add decision starter API for email flows (#4533)

Co-authored-by: hyperswitch-bot[bot] <148525504+hyperswitch-bot[bot]@users.noreply.github.com>

crates/api_models/src/user.rs

@@ -231,3 +231,8 @@ pub enum SignInWithTokenResponse {
     Token(TokenResponse),
     SignInResponse(SignInResponse),
 }
+
+#[derive(Debug, serde::Deserialize, serde::Serialize)]
+pub struct UserFromEmailRequest {
+    pub token: Secret<String>,
+}