feat: Add ES2+ configuration management for carrier-connector

- Add ES2Config struct with base URL, API key, TLS verification, and requester ID fields
- Add LoadES2Config function with default SMDP connection parameters
- Include JSON tags for configuration serialization

apps/carrier-connector/internal/config/config.go

@@ -0,0 +1,17 @@
+package config
+
+type ES2Config struct {
+	BaseURL              string `json:"base_url"`
+	APIKey               string `json:"api_key"`
+	InsecureSkipVerify   bool   `json:"insecure_skip_verify"`
+	FunctionalityRequesterID string `json:"functionality_requester_id"`
+}
+
+func LoadES2Config() *ES2Config {
+	return &ES2Config{
+		BaseURL:                "https://smdp.example.com",
+		APIKey:                 "",
+		InsecureSkipVerify:     true,
+		FunctionalityRequesterID: "telecom-platform",
+	}
+}