[PATCH v1 proxmox-backup] www: percent-encode maintenance mode message to allow commas

[Robert Obkircher <r.obkircher@proxmox.com>]

Commas and equal signs caused problems because the maintenance mode
message is stored in a property string.

With a comma and no quotes (e.g. 'a,b'), the backend failed to update
datastore.cfg because 'read-only,message=a,b' couldn't be re-parsed.
Adding a quote triggered the correct escape logic in the backend, but
then the frontend displayed the mode and message incorrectly. It also
cut off everything after the first equal sign and silently stripped
backslashes.

Percent encoding was chosen because MaintenanceMode::check already
decoded the message. Previously, this potentially caused the error
message to differ from what was displayed in the web UI.

Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
---
I'm not sure if this is a good idea or if we should simply forbid those
characters.

I also tried changing ElementSerializer::serialize_str to quote like 
ElementSerializeSeq, but that wouldn't be sufficient because the parser
in the frontend would still split by comma and parse something like
'read-only,message="a,b"' as type 'b"' and message '"a'.

 www/Utils.js                     | 6 +++++-
 www/window/MaintenanceOptions.js | 5 ++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/www/Utils.js b/www/Utils.js
index fc9a5916..5e1ee0c6 100644
--- a/www/Utils.js
+++ b/www/Utils.js
@@ -800,7 +800,11 @@ Ext.define('PBS.Utils', {
             ([m, msg], pair) => {
                 const [key, value] = pair.split('=');
                 if (key === 'message') {
-                    return [m, value.replace(/^"(.*)"$/, '$1').replace(/\\"/g, '"')];
+                    try {
+                        return [m, decodeURIComponent(value)];
+                    } catch {
+                        return [m, value];
+                    }
                 } else {
                     return [value ?? key, msg];
                 }
diff --git a/www/window/MaintenanceOptions.js b/www/window/MaintenanceOptions.js
index 9a735e5e..e9740843 100644
--- a/www/window/MaintenanceOptions.js
+++ b/www/window/MaintenanceOptions.js
@@ -39,9 +39,8 @@ Ext.define('PBS.window.MaintenanceOptions', {
             if (values.delete === 'maintenance-type') {
                 values.delete = 'maintenance-mode';
             } else if (values['maintenance-type']) {
-                const message = (values['maintenance-msg'] ?? '')
-                    .replaceAll('\\', '')
-                    .replaceAll('"', '\\"');
+                // property string values can't contain symbols like commas and equal signs
+                const message = encodeURIComponent(values['maintenance-msg'] ?? '');
                 const maybe_message = values['maintenance-msg'] ? `,message="${message}"` : '';
                 values['maintenance-mode'] = `type=${values['maintenance-type']}${maybe_message}`;
             }
-- 
2.47.3