enhance(link): Make links be equal on reference only
closes: #22 (closed)
What are the key features of this change
Changes the equals method and the constructor for the link class. The link constructor checks if reference is null or blank and throws an appropriate exception if this is the case. The link equals method returns true for equality if two links have the same reference. This follows the advice that was given in the criteria of the project.
Checklist
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Javadoc -
Relevant tests have been created -
Build tool test passed -
Class version is updated where relevant