Issue:
Bug: [FIX] keymanager config if disabled





Pull request description:
## Type of Change
<!-- Put an `x` in the boxes that apply -->
- [x] Enhancement

## Description
<!-- Describe your changes in detail -->
This fixes unnecessary failure when url and cert for the keymanager is not provided in the config but keymanager is disabled.

## Motivation and Context
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Why is this change required? What problem does it solve?
If it fixes an open issue, please link to the issue here.

If you don't have an issue, we'd recommend starting with one first so the PR
can focus on the implementation (unless it is an obvious bug or documentation fix
that will have little conversation).
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If the keymanager is disabled in the config, there's no reason to provide `url` and `cert` for keymanager since they won't be used. This PR adds a check which checks if keymanager is enabled and only fail for these configs missing if keymanager is enabled

## How did you test it?
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Did you write an integration/unit/API test to verify the code changes?
Or did you test this change manually (provide relevant screenshots)?
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This cannot be tested on any environment


## Checklist
<!-- Put an `x` in the boxes that apply -->

- [x] I formatted the code `cargo +nightly fmt --all`
- [x] I addressed lints thrown by `cargo clippy`
- [x] I reviewed the submitted code

Testing:

This cannot be tested on any environment

Patch:
diff --git a/config/development.toml b/config/development.toml
index 6e56d5bb14d..a607dd94a16 100644
--- a/config/development.toml
+++ b/config/development.toml
@@ -13,7 +13,7 @@ use_xray_generator = false
 bg_metrics_collection_interval_in_secs = 15
 
 [key_manager]
-url = "http://localhost:5000"
+enabled = false
 
 # TODO: Update database credentials before running application
 [master_database]
diff --git a/crates/common_utils/src/types/keymanager.rs b/crates/common_utils/src/types/keymanager.rs
index abcb7aa87f7..078f1f3fcd8 100644
--- a/crates/common_utils/src/types/keymanager.rs
+++ b/crates/common_utils/src/types/keymanager.rs
@@ -25,7 +25,7 @@ use crate::{
 
 #[derive(Debug, Clone)]
 pub struct KeyManagerState {
-    pub enabled: Option<bool>,
+    pub enabled: bool,
     pub url: String,
     pub client_idle_timeout: Option<u64>,
     #[cfg(feature = "km_forward_x_request_id")]
diff --git a/crates/hyperswitch_domain_models/src/type_encryption.rs b/crates/hyperswitch_domain_models/src/type_encryption.rs
index 0ff37b0bc29..983528dee98 100644
--- a/crates/hyperswitch_domain_models/src/type_encryption.rs
+++ b/crates/hyperswitch_domain_models/src/type_encryption.rs
@@ -101,7 +101,7 @@ mod encrypt {
     fn is_encryption_service_enabled(_state: &KeyManagerState) -> bool {
         #[cfg(feature = "encryption_service")]
         {
-            _state.enabled.unwrap_or_default()
+            _state.enabled
         }
         #[cfg(not(feature = "encryption_service"))]
         {
diff --git a/crates/router/src/configs/defaults.rs b/crates/router/src/configs/defaults.rs
index 5719e111759..86bcb687b11 100644
--- a/crates/router/src/configs/defaults.rs
+++ b/crates/router/src/configs/defaults.rs
@@ -12461,16 +12461,3 @@ pub fn get_shipping_required_fields() -> HashMap<String, RequiredFieldInfo> {
         ),
     ])
 }
-
-impl Default for super::settings::KeyManagerConfig {
-    fn default() -> Self {
-        Self {
-            enabled: None,
-            url: String::from("localhost:5000"),
-            #[cfg(feature = "keymanager_mtls")]
-            ca: String::default().into(),
-            #[cfg(feature = "keymanager_mtls")]
-            cert: String::default().into(),
-        }
-    }
-}
diff --git a/crates/router/src/configs/secrets_transformers.rs b/crates/router/src/configs/secrets_transformers.rs
index 8c893b88319..5a204f8508c 100644
--- a/crates/router/src/configs/secrets_transformers.rs
+++ b/crates/router/src/configs/secrets_transformers.rs
@@ -232,14 +232,22 @@ impl SecretsHandler for settings::KeyManagerConfig {
         let keyconfig = value.get_inner();
 
         #[cfg(feature = "keymanager_mtls")]
-        let ca = _secret_management_client
-            .get_secret(keyconfig.ca.clone())
-            .await?;
+        let ca = if keyconfig.enabled {
+            _secret_management_client
+                .get_secret(keyconfig.ca.clone())
+                .await?
+        } else {
+            keyconfig.ca.clone()
+        };
 
         #[cfg(feature = "keymanager_mtls")]
-        let cert = _secret_management_client
-            .get_secret(keyconfig.cert.clone())
-            .await?;
+        let cert = if keyconfig.enabled {
+            _secret_management_client
+                .get_secret(keyconfig.cert.clone())
+                .await?
+        } else {
+            keyconfig.ca.clone()
+        };
 
         Ok(value.transition_state(|keyconfig| Self {
             #[cfg(feature = "keymanager_mtls")]
diff --git a/crates/router/src/configs/settings.rs b/crates/router/src/configs/settings.rs
index 675b8c44e2a..de45252dbf3 100644
--- a/crates/router/src/configs/settings.rs
+++ b/crates/router/src/configs/settings.rs
@@ -213,9 +213,10 @@ pub struct KvConfig {
     pub soft_kill: Option<bool>,
 }
 
-#[derive(Debug, Deserialize, Clone)]
+#[derive(Debug, Deserialize, Clone, Default)]
+#[serde(default)]
 pub struct KeyManagerConfig {
-    pub enabled: Option<bool>,
+    pub enabled: bool,
     pub url: String,
     #[cfg(feature = "keymanager_mtls")]
     pub cert: Secret<String>,
@@ -859,6 +860,8 @@ impl Settings<SecuredSecret> {
             .map(|x| x.get_inner().validate())
             .transpose()?;
 
+        self.key_manager.get_inner().validate()?;
+
         Ok(())
     }
 }
diff --git a/crates/router/src/configs/validations.rs b/crates/router/src/configs/validations.rs
index 67db7b1266c..62b5c08a198 100644
--- a/crates/router/src/configs/validations.rs
+++ b/crates/router/src/configs/validations.rs
@@ -222,3 +222,25 @@ impl super::settings::NetworkTokenizationService {
         })
     }
 }
+
+impl super::settings::KeyManagerConfig {
+    pub fn validate(&self) -> Result<(), ApplicationError> {
+        use common_utils::fp_utils::when;
+
+        #[cfg(feature = "keymanager_mtls")]
+        when(
+            self.enabled && (self.ca.is_default_or_empty() || self.cert.is_default_or_empty()),
+            || {
+                Err(ApplicationError::InvalidConfigurationValueError(
+                    "Invalid CA or Certificate for Keymanager.".into(),
+                ))
+            },
+        )?;
+
+        when(self.enabled && self.url.is_default_or_empty(), || {
+            Err(ApplicationError::InvalidConfigurationValueError(
+                "Invalid URL for Keymanager".into(),
+            ))
+        })
+    }
+}