Improved the test for the InsertAsync method.
Fixed a typo.
Addressed false-negative for the GetHashCode method of Parameter.
Addressed matching names of file and test classes

with the name of product class.
Introduced the GetKeys method.
Implementd the Keys class.
Implemented the GetKeys methods.
Implemented the UpdateaAsync method.
Added the test to ensure throwing exception when addding entity

with duplicated identity.
Addressed code-analysis errors.