ssl: add redirect loop caution to Flexible mode doc (#33132)

* ssl: add redirect loop caution to Flexible mode doc

DEE-3621

- Add :::caution block warning that Flexible mode causes redirect
  loops when the origin forces HTTPS, with links to ERR_TOO_MANY_REDIRECTS
  troubleshooting page and Enforce HTTPS connections guide

* ssl: cross-link Enforce HTTPS guide from redirect loop troubleshooting

DEE-3621

Author: ngayerie

src/content/docs/ssl/origin-configuration/ssl-modes/flexible.mdx

@@ -46,6 +46,14 @@ Choose this option when you cannot set up an SSL certificate on your origin or y
 
 ## Limitations
 
+:::caution
+
+If your origin forces HTTPS by automatically redirecting HTTP requests to HTTPS, do not use Flexible mode. Because Cloudflare connects to your origin over HTTP, this creates a redirect loop that makes your site inaccessible. Use [**Full**](/ssl/origin-configuration/ssl-modes/full/) or [**Full (strict)**](/ssl/origin-configuration/ssl-modes/full-strict/) mode instead.
+
+Refer to [ERR_TOO_MANY_REDIRECTS](/ssl/troubleshooting/too-many-redirects/) for troubleshooting guidance, or [Enforce HTTPS connections](/ssl/edge-certificates/encrypt-visitor-traffic/) to redirect traffic to HTTPS at the Cloudflare edge without setting up redirects at your origin.
+
+:::
+
 Flexible mode is only supported for HTTPS connections on port 443 (default port). Other ports using HTTPS will fall back to [**Full** mode](/ssl/origin-configuration/ssl-modes/full/).
 
 If your application contains sensitive information (personalized data, user login), use [**Full**](/ssl/origin-configuration/ssl-modes/full/) or [**Full (Strict)**](/ssl/origin-configuration/ssl-modes/full-strict/) modes instead.

src/content/docs/ssl/troubleshooting/too-many-redirects.mdx

@@ -69,7 +69,7 @@ end
 
 <br />
 
-To solve this issue, either remove HTTPS redirects from your origin server or update your SSL/TLS Encryption Mode to be [**Full**](/ssl/origin-configuration/ssl-modes/full/) or higher (requires an SSL certificate configured at your origin server).
+To solve this issue, either remove HTTPS redirects from your origin server or update your SSL/TLS Encryption Mode to be [**Full**](/ssl/origin-configuration/ssl-modes/full/) or higher (requires an SSL certificate configured at your origin server). To enforce HTTPS at the Cloudflare edge without setting up redirects at your origin, refer to [Enforce HTTPS connections](/ssl/edge-certificates/encrypt-visitor-traffic/).
 
 ### Full or Full (strict) encryption mode