Register v0.2.3 #55

@JuliaRegistrator register

Release notes:

• Second derivatives (∇∇, Δ) on skeleton integrals: jump(∇∇(u)), mean(∇∇(u)), mean(Δ(u)), … of the unknown, test and trial functions are compiled by the facet kernels (C⁰ interior-penalty terms, Hessian-jump regularisations ⟦∇∇u⟧:⟦∇∇v⟧), with the Hessian push-forward of each side (its Jt⁻¹ and the curvature of its cell map: exact on non-affine quadrilaterals and hexahedra); residual, assembled and matrix-free Jacobian. They no longer send the skeleton to the Gridap fallback.
• KernelFunctional evaluates skeleton integrals with the facet kernels (energies of jump penalties such as ½ ∫ c ⟦∇u⟧:⟦∇u⟧ dΛ and ½ ∫ c ⟦∇∇u⟧:⟦∇∇u⟧ dΛ, used by the Armijo line search; :min/:max over the facet points). Before, those terms were summed by the Gridap fallback.
• CI: the Hessian tests run in their own job (HFK_TEST_GROUP=hessian).

This is the last release on Gridap 0.19.9; the next one moves to Gridap 0.20.