Issue:
Bug: refactor: alter query for merchant scoped metadata



Remove `is_null` from `find_merchant_scoped_dashboard_metadata`
This is done to make DB changes and support backward compatibility in next deployment.

Pull request description:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [ ] Enhancement
- [x] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
Alter query in `find_merchant_scoped_dashboard_metadata`
For merchant scoped metadata it need not to be considered whether user_id column is `null` or not


### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

<!--
Provide links to the files with corresponding changes.

Following are the paths where you can find config files:
1. `config`
2. `crates/router/src/configs`
3. `loadtest/config`
-->


## Motivation and Context
Closes #5396


## How did you test it?
To get the metadata use curl:
```
curl --location 'http://localhost:8080/user/data?keys=ProductionAgreement%2CSetupProcessor%2CConfigureEndpoint%2CSetupComplete%2CFirstProcessorConnected%2CSecondProcessorConnected%2CConfiguredRouting%2CTestPayment%2CIntegrationMethod%2CConfigurationType%2CIntegrationCompleted%2CStripeConnected%2CPaypalConnected%2CSPRoutingConfigured%2CFeedback%2CProdIntent%2CSPTestPayment%2CDownloadWoocom%2CConfigureWoocom%2CSetupWoocomWebhook%2CIsMultipleConfiguration%2CIsChangePasswordRequired' \
--header 'Authorization: Bearer JWT'
```

In response we will get the metadata both that set or unset:
```
[
    {
        "ProductionAgreement": false
    },
    {
        "SetupProcessor": null
    },
    {
        "ConfigureEndpoint": false
    },
    {
        "SetupComplete": false
    },
    {
        "FirstProcessorConnected": null
    },
    {
        "SecondProcessorConnected": null
    },
    {
        "ConfiguredRouting": null
    },
    {
        "TestPayment": null
    },
    {
        "IntegrationMethod": {
            "integration_type": "test_type"
        }
    },
    {
        "ConfigurationType": null
    },
    {
        "IntegrationCompleted": true
    },
    {
        "StripeConnected": null
    },
    {
        "PaypalConnected": null
    },
    {
        "SPRoutingConfigured": null
    },
    {
        "Feedback": {
            "email": "sam234563@gmail.com",
            "description": "Test Feedback",
            "rating": 5,
            "category": "test"
        }
    },
    {
        "ProdIntent": null
    },
    {
        "SPTestPayment": false
    },
    {
        "DownloadWoocom": false
    },
    {
        "ConfigureWoocom": false
    },
    {
        "SetupWoocomWebhook": false
    },
    {
        "IsMultipleConfiguration": false
    },
    {
        "IsChangePasswordRequired": false
    }
]
```

## 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
- [ ] I added unit tests for my changes where possible


Testing:
To get the metadata use curl:
```
curl --location 'http://localhost:8080/user/data?keys=ProductionAgreement%2CSetupProcessor%2CConfigureEndpoint%2CSetupComplete%2CFirstProcessorConnected%2CSecondProcessorConnected%2CConfiguredRouting%2CTestPayment%2CIntegrationMethod%2CConfigurationType%2CIntegrationCompleted%2CStripeConnected%2CPaypalConnected%2CSPRoutingConfigured%2CFeedback%2CProdIntent%2CSPTestPayment%2CDownloadWoocom%2CConfigureWoocom%2CSetupWoocomWebhook%2CIsMultipleConfiguration%2CIsChangePasswordRequired' \
--header 'Authorization: Bearer JWT'
```

In response we will get the metadata both that set or unset:
```
[
    {
        "ProductionAgreement": false
    },
    {
        "SetupProcessor": null
    },
    {
        "ConfigureEndpoint": false
    },
    {
        "SetupComplete": false
    },
    {
        "FirstProcessorConnected": null
    },
    {
        "SecondProcessorConnected": null
    },
    {
        "ConfiguredRouting": null
    },
    {
        "TestPayment": null
    },
    {
        "IntegrationMethod": {
            "integration_type": "test_type"
        }
    },
    {
        "ConfigurationType": null
    },
    {
        "IntegrationCompleted": true
    },
    {
        "StripeConnected": null
    },
    {
        "PaypalConnected": null
    },
    {
        "SPRoutingConfigured": null
    },
    {
        "Feedback": {
            "email": "sam234563@gmail.com",
            "description": "Test Feedback",
            "rating": 5,
            "category": "test"
        }
    },
    {
        "ProdIntent": null
    },
    {
        "SPTestPayment": false
    },
    {
        "DownloadWoocom": false
    },
    {
        "ConfigureWoocom": false
    },
    {
        "SetupWoocomWebhook": false
    },
    {
        "IsMultipleConfiguration": false
    },
    {
        "IsChangePasswordRequired": false
    }
]
```

Patch:
diff --git a/crates/diesel_models/src/query/dashboard_metadata.rs b/crates/diesel_models/src/query/dashboard_metadata.rs
index 6f88629d82a..725a95ffef3 100644
--- a/crates/diesel_models/src/query/dashboard_metadata.rs
+++ b/crates/diesel_models/src/query/dashboard_metadata.rs
@@ -87,9 +87,8 @@ impl DashboardMetadata {
         org_id: String,
         data_types: Vec<enums::DashboardMetadata>,
     ) -> StorageResult<Vec<Self>> {
-        let predicate = dsl::user_id
-            .is_null()
-            .and(dsl::merchant_id.eq(merchant_id))
+        let predicate = dsl::merchant_id
+            .eq(merchant_id)
             .and(dsl::org_id.eq(org_id))
             .and(dsl::data_key.eq_any(data_types));
 
diff --git a/crates/router/src/db/dashboard_metadata.rs b/crates/router/src/db/dashboard_metadata.rs
index 5267985e1ac..df36eb85ec0 100644
--- a/crates/router/src/db/dashboard_metadata.rs
+++ b/crates/router/src/db/dashboard_metadata.rs
@@ -276,8 +276,7 @@ impl DashboardMetadataInterface for MockDb {
         let query_result = dashboard_metadata
             .iter()
             .filter(|metadata_inner| {
-                metadata_inner.user_id.is_none()
-                    && metadata_inner.merchant_id == merchant_id
+                metadata_inner.merchant_id == merchant_id
                     && metadata_inner.org_id == org_id
                     && data_keys.contains(&metadata_inner.data_key)
             })