feat(client): Support body placeholder for SSH endpoints (#1286)

* feat(ssh): Add BODY placeholder support for SSH endpoints

- Modify ExecuteSSHCommand to capture stdout output
- Update SSH endpoint handling to use needsToReadBody() mechanism
- Add comprehensive test cases for SSH BODY functionality
- Support basic body content, pattern matching, JSONPath, and functions
- Maintain backward compatibility with existing SSH endpoints

* docs: Add SSH BODY placeholder examples to README

- Add [BODY] placeholder to supported SSH placeholders list
- Add comprehensive examples showing various SSH BODY conditions
- Include pattern matching, length checks, JSONPath expressions
- Demonstrate function wrappers (len, has, any) usage

* Revert "docs: Add SSH BODY placeholder examples to README"

This reverts commit ae93e38683.

* docs: Add [BODY] placeholder to SSH supported placeholders list

* test: remove SSH BODY placeholder test cases

* Update client/client.go

* Update client/client.go

* docs: Add minimal SSH BODY example

---------

Co-authored-by: TwiN <twin@linux.com>

README.md

@@ -3031,12 +3031,13 @@ endpoints:
       password: "password"
     body: |
       {
-        "command": "uptime"
+        "command": "echo '{\"memory\": {\"used\": 512}}'"
       }
     interval: 1m
     conditions:
       - "[CONNECTED] == true"
       - "[STATUS] == 0"
+      - "[BODY].memory.used > 500"
 ```
 
 you can also use no authentication to monitor the endpoint by not specifying the username
@@ -3059,6 +3060,7 @@ endpoints:
 The following placeholders are supported for endpoints of type SSH:
 - `[CONNECTED]` resolves to `true` if the SSH connection was successful, `false` otherwise
 - `[STATUS]` resolves the exit code of the command executed on the remote server (e.g. `0` for success)
+- `[BODY]` resolves to the stdout output of the command executed on the remote server
 - `[IP]` resolves to the IP address of the server
 - `[RESPONSE_TIME]` resolves to the time it took to establish the connection and execute the command