Breakable parbox at the end of page

Question

if I'll do

\documentclass[a4paper]{article}
\usepackage{lipsum}
\begin{document}
\parbox{\columnwidth}{\lipsum[1-20]}
\end{document}

it outputs

Is there any way to get a breakable parbox? If not, I will need something different. In that specific setting I only need to do:

\documentclass[a4paper]{article}
\usepackage{calc}
\usepackage{lipsum}
\begin{document}
\textbf{Proof}\par
\noindent\hspace{5mm}\parbox{\columnwidth-10mm}{\lipsum[1-20]}\\
$_{}$\hfill$\square$
\end{document}

Ty'all.

Answer 1

For those already invested in tcolorbox (and those yet to make up their minds):

\documentclass[a4paper]{article}
\usepackage[nopar]{lipsum}
\usepackage{tcolorbox}
\tcbuselibrary{breakable}

\begin{document}

\lipsum[1]

\begin{tcolorbox}[breakable,colback=white,colframe=white]
  \lipsum[1-20]
\end{tcolorbox}

\lipsum[1]

\end{document}

Answer 2

Solution: going to tcolorbox or mdframed. Possible solution is offered through:

\begin{mdframed}[leftmargin=5mm, linewidth=0pt, skipbelow=0pt]
text
\end{mdframed}