Update existing routes:

GET /svn/:id

{
    "id": int,
    ...
    "settings": {
        "commit_rules": {
            "mandatory_reference": boolean,
            "allow_commit_message_change": boolean
        },

        "access_file": "[/]\n* = \nContributors = r\n[/stuff]\nContributors = rw"
    }
}

• As JSON doesn't support multi-line strings, the multiline is defined here with an array which each line corresponds to a line of svn access file
• The content of "access_file" key corresponds to what is customizable by svn administrators in "Access control" tab in the web UI (it means that the global definition of [groups] as well as default [/] is not visible nor modifiable here but will be present at the begining of the final file anyway.

POST /svn

{
    ...
    "settings": {
        "commit_rules": {
            "mandatory_reference": boolean,
            "allow_commit_message_change": boolean
        },

        "access_file": "[/]\n* = \nContributors = r\n[/stuff]\nContributors = rw"
    }
}

PUT /svn/:id

{
    "id": int
    "settings": {
        "commit_rules": {
            "mandatory_reference": boolean,
            "allow_commit_message_change": boolean
        },

        "access_file": "[/]\n* = \nContributors = r\n[/stuff]\nContributors = rw"
    }
}

• Changes are recorded in Project History (link to svn access file history)