Format abstracts as unnumbered chapters

Question

I'm writing master thesis and working on LaTeX template for the successors ...

The standard of the university requires abstract in every language to be formed as unnumbered Chapter:

\chapter*{Abstract}
\addcontentsline{toc}{chapter}{Abstract}
...
\chapter*{Résumé}
\addcontentsline{toc}{chapter}{Résumé}
...

Is it possible to customize the abstract environment (or to use other workaround) to be able to write:

{
\selectlanguage{russian}
\begin{abstract}
    This is ABSTRAAAAACT!!!
\end{abstract}
}
{
\selectlanguage{french}
\begin{abstract}
    This is ABSTRAAAAACT!!!
\end{abstract}
}

So that the titles would still appear in the ToC as unnumbered chapters?

P.S. I'm using the report class

Answer 1

This just makes abstract include a chapter named with the command \abstractname, which is provided by babel and is re-defined for each language.

The lipsum package and \lipsum command are used only to provide some dummy text.

\documentclass{book}

\usepackage{lipsum}
\usepackage[english,french]{babel}

%% START HERE %%
\def\abstract{
  \chapter*{\abstractname} % start chapter
  \addcontentsline{toc}{chapter}{\abstractname} % table of contents line
  \markboth{\MakeUppercase{\abstractname}}{} % header mark
}
\def\endabstract{\clearpage}
%% END HERE %%

\begin{document}

\selectlanguage{english}

\tableofcontents

\begin{abstract}
\lipsum[1-20]
\end{abstract}

\selectlanguage{french}

\begin{abstract}
\lipsum[1-20]
\end{abstract}

\end{document}