Implementation of nilpotent Lie groups as manifolds with a distinguished global coordinate system (exponential coordinates).

Planned features:

• representation of elements in exponential coordinates of the first or second kind
• multiplication of symbolic points (using the manifold point framework)
• the frames of left-invariant and right-invariant vector fields
• the exponential map exp:\mathfrak{g}\to G and the logarithm
• the adjoint map Ad:G\times \mathfrak{g}\to\mathfrak{g}

Depends on #26080

CC: @tscrim @egourgoulhon

Component: group theory

Keywords: Lie groups, Lie algebras, nilpotent

Author: Eero Hakavuori

Branch: b2ef2d9

Reviewer: Eric Gourgoulhon, Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/26344