Fix Sonar’s “Make Transient or Serializable” Warning in Java

SonarQube's java:S1948 rule flags fields in Serializable classes that are neither transient nor Serializable themselves, preventing NotSerializableException at runtime. Four strategies are covered: making the nested class implement Serializable (preferred for core state), declaring fields static (ideal for loggers and constants), using the transient keyword (for temporary or non-serializable fields), and handling Spring framework dependencies by marking injected services as transient. The transient approach requires re-initializing fields via readObject upon deserialization. For third-party non-serializable classes, wrapping in a DTO or using custom writeObject/readObject methods are recommended.