Custom proof environment preserving optional argument

I basically want to obtain the result (replace Proof -> Solution, and mdframed around the environemnt) simply by the code:

begin{solution}
    Set Theory Best Theory.
    begin{align*}
        2 = {emptyset,{emptyset},{emptyset,{emptyset}}}
    end{align*}
end{solution}

This can be easily done using renewenvironment. My main issue lies in preserving the optional argument in the proof environment, i.e. something like this would still work:

begin{solution}[Proof]
    Set Theory Best Theory.
    begin{align*}
        2 = {emptyset,{emptyset},{emptyset,{emptyset}}}
    end{align*}
end{solution}

Any help is greatly appreciated.

EDIT: To clarify, I do not have a working solution environment working. The first image above can be made possible by:

newenvironment{solution}
  {begin{mdframed}begin{proof}[Solution]}
  {end{proof}end{mdframed}}

But it will not accept any arguments (so the second image will not be obtained)

newenvironment{solution}[1][Solution]
  {begin{mdframed}begin{proof}[#1]}
  {end{proof}end{mdframed}}