If using `method=:newton` with `linesearch=LineSearches.Static()` (the default linesearch), an additional argument
`project_region!` (default value `(x)->(nothing)`) can be used to define a function to modify the proposed new
`x` value after each Newton iteration.

For example, `project_region! = (x) -> (x .= max.(x, 1e-80))` will enforce a constraint `x[i] >= 1e-80`.

If `method = :newton` and `linesearch=LineSearches.Static()` (the default),
an additional argument `apply_step!` (default value `(x, x_old, newton_step)->(x .= x_old .+ newton_step)`)
can be used to define a function to modify the proposed new `x` value after the Newton iteration.
eg
    `apply_step! = (x, x_old, newton_step)->(x .= x_old .+ newton_step; x .= max.(x, 1e-80))`
will enforce a constraint `x[i] >= 1e-80`.