Returns EncryptionMaterials which the caller can use for encryption.
Each implementation of EncryptionMaterialsProvider can choose its own
strategy for loading encryption material. For example, an
implementation might load encryption material from an existing key
management system, or load new encryption material when keys are
Forces this encryption materials provider to refresh its encryption
material. For many implementations of encryption materials provider,
this may simply be a no-op, such as any encryption materials provider
implementation that vends static/non-changing encryption material.
For other implementations that vend different encryption material
throughout their lifetime, this method should force the encryption
materials provider to refresh its encryption material.