Antipattern: Use Dual-Purpose Foreign Key
A solution for these cases has become popular enough to be given a name, Polymorphic Associations. This is also sometimes called a promiscuous association, because it references multiple tables.
Defining a Polymorphic Association
To make Polymorphic Associations work, you must add an extra string column alongside the foreign key on issue_id. The extra column contains the name of the parent table referenced by the current row.
In this example, the new column is called issue_type, and contains a string value, either Bugs or FeatureRequests, corresponding to the names of the two possible parent tables in this association.
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