fix: add omitempty to Account.Status field (#48)

Some strict ACME CAs reject requests that include an empty status field.
Adding omitempty ensures the status field is omitted when empty, which
aligns with the spec note that clients need NOT set this field when
creating a new account.

Co-authored-by: Goll.Wang <goll.wang@trustasia.com>

Author: go-goll

acme/account.go

@@ -38,7 +38,7 @@ type Account struct {
 	// initiated deactivation.  See Section 7.1.6.
 	//
 	// The client need NOT set this field when creating a new account.
-	Status string `json:"status"`
+	Status string `json:"status,omitempty"`
 
 	// contact (optional, array of string):  An array of URLs that the
 	// server can use to contact the client for issues related to this