FlowRegEnvCost 0.1.2

Maintenance release addressing the CRAN check NOTEs. No user-visible changes to the package functionality.

• Added an Authors@R field to DESCRIPTION, replacing the free-text Author and Maintainer fields.
• Updated inst/CITATION to use bibentry() and c(person(...)) instead of the deprecated citEntry() and personList().
• flowdata: the DOI in the \source section now uses \doi{} markup instead of a \url{} link.
• flowdata: fixed lost braces in the \format section by marking up the flow units as \eqn{m^{3}}{m^3}/s.