Issue:
Bug: Throw an error when outgoing webhook events env var not found





Pull request description:


## Type of Change
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- [ ] Bugfix
- [ ] New feature
- [x] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
Throw an error when outgoing webhook events env var not found


### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

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2. `crates/router/src/configs`
3. `loadtest/config`
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## Motivation and Context
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## How did you test it?
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## Checklist
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- [ ] I formatted the code `cargo +nightly fmt --all`
- [ ] I addressed lints thrown by `cargo clippy`
- [ ] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible
- [ ] I added a [CHANGELOG](/CHANGELOG.md) entry if applicable


Testing:

Patch:
diff --git a/crates/router/src/services/kafka.rs b/crates/router/src/services/kafka.rs
index 2b29a61b4a4..2bcfcfe974f 100644
--- a/crates/router/src/services/kafka.rs
+++ b/crates/router/src/services/kafka.rs
@@ -126,6 +126,15 @@ impl KafkaSettings {
             ))
         })?;
 
+        common_utils::fp_utils::when(
+            self.outgoing_webhook_logs_topic.is_default_or_empty(),
+            || {
+                Err(ApplicationError::InvalidConfigurationValueError(
+                    "Kafka Outgoing Webhook Logs topic must not be empty".into(),
+                ))
+            },
+        )?;
+
         Ok(())
     }
 }