doc: add telemetry command name restrictions

Telemetry command names must contain only alphanumeric characters
(`A-Z`, `a-z`, `0-9`), underscore (`_`), and forward slash (`/`).
Other characters, including hyphens (`-`), are not allowed and
cause registration to fail.

This patch updates the documentation to explicitly state these
restrictions and highlights the existing invalid example
"/l3fwd-power/stats" (in l3fwd-power app).

Signed-off-by: Sivaprasad Tummala <[email protected]>
Acked-by: Bruce Richardson <[email protected]>

Author: sivapt12

doc/guides/prog_guide/telemetry_lib.rst

@@ -157,6 +157,11 @@ command. An example command being registered is shown below:
     rte_telemetry_register_cmd("/example_lib/string_example", handle_string,
             "Returns an example string. Takes no parameters");
 
+The command name **must consist only of alphanumeric characters (`A-Z`, `a-z`, `0-9`)
+and the special characters underscore (`_`) and forward slash (`/`)**.
+Any other characters, including spaces, are not permitted
+and will cause the command registration to fail.
+
 
 Using Commands
 --------------