Add the following to the apache config file inside the https virtual host:
<Location /svn>
DAV svn
SVNAutoversioning on
SVNParentPath /home/svn
AuthzSVNAccessFile /home/svn/.svnaccess
Satisfy Any
Require valid-user
AuthType Basic
AuthName "Subversion Repository"
AuthUserFile /etc/apache2/httpusers
</Location>
The .svnaccess file has the following format (repo is an SVN repository located in /home/svn/repo):
[groups]
developers = user1, user2
[repo:/]
@developers = rw
user3 = r
[repo:/subdir]
user4 = rw