Refactored and added client credentials flow

internal/flows/client_credentials.go

@@ -0,0 +1,29 @@
+package flows
+
+import (
+	opaal "davidallendj/opaal/internal"
+	"fmt"
+)
+
+func ClientCredentials(config *opaal.Config, server *opaal.Server, client *opaal.Client) error {
+	// register a new OAuth 2 client with authorization srever
+	_, err := client.RegisterOAuthClient(config.ActionUrls.RegisterClient, nil)
+	if err != nil {
+		return fmt.Errorf("failed to register OAuth client: %v", err)
+	}
+
+	// authorize the client
+	_, err = client.AuthorizeClient(config.ActionUrls.AuthorizeClient)
+	if err != nil {
+		return fmt.Errorf("failed to authorize client: %v", err)
+	}
+
+	// request a token from the authorization server
+	res, err := client.FetchTokenFromAuthorizationServer(config.ActionUrls.AccessToken, "", nil)
+	if err != nil {
+		return fmt.Errorf("failed to fetch token from authorization server: %v", err)
+	}
+
+	fmt.Printf("token: %v\n", string(res))
+	return nil
+}