Handle expired agreements and rewrite README

- Implement robust End User Agreement expiry detection and handling
- Add graceful error recovery for failed accounts
- Rewrite README.md to focus on user benefits
- Add documentation guidelines to AGENTS.md

gocardless-client/src/client.rs

@@ -3,7 +3,7 @@ use reqwest_middleware::ClientWithMiddleware;
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
 use tracing::{debug, instrument};
-use crate::models::{TokenResponse, PaginatedResponse, Requisition, Account, TransactionsResponse};
+use crate::models::{TokenResponse, PaginatedResponse, Requisition, Account, TransactionsResponse, EndUserAgreement};
 
 #[derive(Error, Debug)]
 pub enum GoCardlessError {
@@ -92,6 +92,39 @@ impl GoCardlessClient {
         self.get_authenticated(url).await
     }
 
+    #[instrument(skip(self))]
+    pub async fn get_agreements(&self) -> Result<PaginatedResponse<EndUserAgreement>, GoCardlessError> {
+        let url = self.base_url.join("/api/v2/agreements/enduser/")?;
+        self.get_authenticated(url).await
+    }
+
+    #[instrument(skip(self))]
+    pub async fn get_agreement(&self, id: &str) -> Result<EndUserAgreement, GoCardlessError> {
+        let url = self.base_url.join(&format!("/api/v2/agreements/enduser/{}/", id))?;
+        self.get_authenticated(url).await
+    }
+
+    #[instrument(skip(self))]
+    pub async fn is_agreement_expired(&self, agreement_id: &str) -> Result<bool, GoCardlessError> {
+        let agreement = self.get_agreement(agreement_id).await?;
+
+        // If not accepted, it's not valid
+        let Some(accepted_str) = agreement.accepted else {
+            return Ok(true);
+        };
+
+        // Parse acceptance date
+        let accepted = chrono::DateTime::parse_from_rfc3339(&accepted_str)
+            .map_err(|e| GoCardlessError::ApiError(format!("Invalid date format: {}", e)))?
+            .with_timezone(&chrono::Utc);
+
+        // Get validity period (default 90 days)
+        let valid_days = agreement.access_valid_for_days.unwrap_or(90) as i64;
+        let expiry = accepted + chrono::Duration::days(valid_days);
+
+        Ok(chrono::Utc::now() > expiry)
+    }
+
     #[instrument(skip(self))]
     pub async fn get_account(&self, id: &str) -> Result<Account, GoCardlessError> {
         let url = self.base_url.join(&format!("/api/v2/accounts/{}/", id))?;