MigrationVersion
A migration's version, ordered the way version numbers are ordered rather than the way text is.
1.9 comes before 1.10. Parts are held as Long, so a version written as a timestamp - 20260827120000 - fits.
Missing parts are zero, so 1, 1.0 and 1.0.0 are one version, not three. They compare equal, they hash alike, and two migrations carrying them are a duplicate rather than a sequence. text keeps whichever of them was actually written; canonical is the spelling that goes into the history table.