add credential checking to api

Sources/StudentVue/Extensions/XMLHash+parse.swift

@@ -24,11 +24,15 @@ public extension XMLHash {
         do {
             for child in request.children {
                 for attr in XMLHash.errorAttributes {
-                    guard let attrValue = child.element?.attribute(by: attr)?.text else {
+                    guard let attrValue = child.element?.attribute(by: attr)?.text.lowercased() else {
                         continue
                     }
 
-                    throw StudentVueApi.StudentVueErrors.soapError(attrValue)
+                    if attrValue.contains("user id") || attrValue.contains("password") {
+                        throw StudentVueApi.StudentVueErrors.invalidCredentials
+                    } else {
+                        throw StudentVueApi.StudentVueErrors.soapError(attrValue)
+                    }
                 }
             }
         } catch let error as StudentVueApi.StudentVueErrors {

Sources/StudentVue/SOAPApi/StudentVueApi.swift

@@ -177,6 +177,23 @@ public class StudentVueApi {
         return try XMLHash.parse(soapString: result)
     }
 
+    ///  Checks validity of user credentials quickly
+    ///
+    ///  - Throws: `Error` some other error has occured when api request was sent
+    ///
+    ///  - Returns: Success or not
+    public func checkCredentials() async throws -> Bool {
+        do {
+            _ = try await xmlServiceRequest(methodName: .getSoundFileData)
+
+            return true
+        } catch StudentVueErrors.invalidCredentials {
+            return false
+        } catch {
+            throw error
+        }
+    }
+
     /// Gets districts near the given zip code
     ///
     /// - Parameter zip: The zip code to search for near-by districts that use StudentVue

Sources/StudentVue/SOAPApi/StudentVueErrors.swift

@@ -14,6 +14,7 @@ extension StudentVueApi {
         case clientNotIntialised
         case noUsername
         case noPassword
+        case invalidCredentials
         case soapError(String)
     }
 }
@@ -31,6 +32,8 @@ extension StudentVueApi.StudentVueErrors {
             return "No username provided"
         case .noPassword:
             return "No password provided"
+        case .invalidCredentials:
+            return "Invalid user id or password"
         case .soapError(let string):
             return "Soap request returned error: \(string)"
         }