where a link opens should not be decided by the server but by you, the client.
it was a bad habit / sin of the 90's, when each website decided to do it differently.
nowadays the natural expectation is "a link opens in the same window unless the client on itself modifies that behaviour".
there are countless options in browsers and/or addons for clients available
which let you configure the link opening/tabbing behaviour in all details,
including individually per-site.
please do not let the 90's sins come back!
it was a bad habit / sin of the 90's, when each website decided to do it differently.
nowadays the natural expectation is "a link opens in the same window unless the client on itself modifies that behaviour".
there are countless options in browsers and/or addons for clients available
which let you configure the link opening/tabbing behaviour in all details,
including individually per-site.
please do not let the 90's sins come back!