Migrate /create-fee-bump endpoint from REST to GraphQL

internal/serve/graphql/resolvers/errors.go

@@ -0,0 +1,27 @@
+// GraphQL resolver error message constants
+package resolvers
+
+// Error message constants
+const (
+	// RegisterAccount errors
+	ErrMsgAccountAlreadyExists      = "Account is already registered"
+	ErrMsgInvalidAddress            = "Invalid address: must be a valid Stellar public key or contract address"
+	ErrMsgAccountRegistrationFailed = "Failed to register account: %s"
+
+	// DeregisterAccount errors
+	ErrMsgAccountNotFound             = "Account not found"
+	ErrMsgAccountDeregistrationFailed = "Failed to deregister account: %s"
+	ErrMsgAccountDeregisteredSuccess  = "Account deregistered successfully"
+
+	// BuildTransaction errors
+	ErrMsgInvalidOperations         = "Invalid operations: %s"
+	ErrMsgInvalidTransactionData    = "Invalid TransactionData: %s"
+	ErrMsgTransactionBuildFailed    = "Failed to build transaction"
+	ErrMsgChannelAccountUnavailable = "unable to assign a channel account"
+
+	// CreateFeeBumpTransaction errors
+	ErrMsgCouldNotParseTransactionEnvelope = "Could not parse transaction envelope."
+	ErrMsgCannotWrapFeeBumpTransaction     = "Cannot wrap a fee-bump transaction into another fee-bump transaction"
+	ErrMsgInvalidTransaction               = "Transaction is not a valid transaction"
+	ErrMsgFeeBumpCreationFailed            = "Failed to create fee bump transaction: %s"
+)