Instead of using the field FieldData.Raw, use method GetOkError() which does
type conversion but still allows to check whether a value for the parameter was
provided. Note that GetOkError() converts nil values to default or zero values,
so, for example, a nil plaintext value will result in the empty string being
encrypted.
* Enforce Minimum cache size for transit backend
* enfore minimum cache size and log a warning during backend construction
* Update documentation for transit backend cache configuration
* Added changelog
* Addressed review feedback and added unit test
* Modify code in pathCacheConfigWrite to make use of the updated cache size
* Updated code to refresh cache size on transit backend without restart
* Update code to acquire read and write locks appropriately
