[PATCH backup v4 2/4] docs: client: document further password constrains

[Maximiliano Sandoval <m.sandoval@proxmox.com>]

Even though newlines are control characters, we keep them explicitly for ease of
understanding.

Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
---
 docs/backup-client.rst | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/docs/backup-client.rst b/docs/backup-client.rst
index e2a05d4fc..cd7488287 100644
--- a/docs/backup-client.rst
+++ b/docs/backup-client.rst
@@ -168,9 +168,10 @@ Environment Variables
    wireguard, instead of using an HTTP proxy.
 
 
-.. Note:: Passwords must be valid UTF-8 and may not contain newlines. For your
-   convenience, Proxmox Backup Server only uses the first line as password, so
-   you can add arbitrary comments after the first newline.
+.. Note:: Passwords must be valid UTF-8 and may not contain newlines or any
+   control character. For your convenience, Proxmox Backup Server only uses the
+   first line as password, so you can add arbitrary comments after the first
+   newline.
 
 
 System and Service Credentials
-- 
2.47.3