Hugin used to use the lensfun database. But the 2015 version of Hugin's release notes state:
Hugin now has its own camera and lens database, and hugin_lensdb is the maintenance tool.
Lens data is automatically added to the database when stitching a project file from hugin. Data can also be manually added to the database from hugin and from Calibrate_Lens_GUI.
Lens data can be applied to a project in the same manner as previously, in the Photos tab, select an image with right mouse to bring up the context menu and select Lens → Load lens from lens database.
For database maintenance see
hugin_lensdb -h, or
man hugin_lensdb (Linux and OSX) for details on usage.
On my OSX installation of the 2018 version of Hugin, the calibrate_len_gui.app is in the Applications/Hugin folder, next to Hugin.app, HuginStitchProject.app, and PTBatcherGUI.app. hugin_lens_db lives in the usual Hugin.app packaged Contents/MacOS folder, with aliases in the Hugin/tools_mac folder (outside the package).