chore(security): Make the warning for the deprecated OpenSSL provider more verbose (vectordotdev#18278)

* chore(security): Make the warning for the deprecated OpenSSL provider more verbose

To guide users that run into it.

Signed-off-by: Jesse Szwedko <[email protected]>

* style

Signed-off-by: Jesse Szwedko <[email protected]>

---------

Signed-off-by: Jesse Szwedko <[email protected]>

Author: jszwedko

src/app.rs

@@ -572,7 +572,7 @@ pub fn init_logging(color: bool, format: LogFormat, log_level: &str, rate: u64)
 /// The returned [Provider] must stay in scope for the entire lifetime of the application, as it
 /// will be unloaded when it is dropped.
 pub fn load_openssl_legacy_providers() -> Result<Vec<Provider>, ExitCode> {
-    warn!(message = "DEPRECATED The openssl legacy provider provides algorithms and key sizes no longer recommended for use.");
+    warn!(message = "DEPRECATED The openssl legacy provider provides algorithms and key sizes no longer recommended for use. Set `--openssl-legacy-provider=false` or `VECTOR_OPENSSL_LEGACY_PROVIDER=false` to disable. See https://vector.dev/highlights/2023-08-15-0-32-0-upgrade-guide/#legacy-openssl for details.");
     ["legacy", "default"].into_iter().map(|provider_name| {
         Provider::try_load(None, provider_name, true)
             .map(|provider| {