[BUG] App Configuration spring.cloud.azure.appconfiguration.stores[0].connection-string is validated when spring.cloud.azure.appconfiguration.enabled is false

[yanivnahoum]

Describe the bug
spring.cloud.azure.appconfiguration.stores[0].connection-string is validated when spring.cloud.azure.appconfiguration.enabled is false
The connection string, being a secret, is typically specified from outside (program argument, env var, etc).
When running tests, and when running the app locally with feature flags under feature-management.feature-flags, spring.cloud.azure.appconfiguration.enabled is false and the connection string is left empty. The connection string should not have to be specified and should not be validated since it's not needed in these cases.

Exception or Stack Trace

19:40:46.412 ERROR main o.s.b.SpringApplication Application run failed 
java.lang.IllegalStateException: Unable to load config data from 'azureAppConfiguration'
	at org.springframework.boot.context.config.StandardConfigDataLocationResolver.getReferences(StandardConfigDataLocationResolver.java:142)
	at org.springframework.boot.context.config.StandardConfigDataLocationResolver.getReferences(StandardConfigDataLocationResolver.java:127)
	at org.springframework.boot.context.config.StandardConfigDataLocationResolver.resolve(StandardConfigDataLocationResolver.java:120)
	at org.springframework.boot.context.config.ConfigDataLocationResolvers.lambda$resolve$1(ConfigDataLocationResolvers.java:102)
	at org.springframework.boot.context.config.ConfigDataLocationResolvers.resolve(ConfigDataLocationResolvers.java:113)
	at org.springframework.boot.context.config.ConfigDataLocationResolvers.resolve(ConfigDataLocationResolvers.java:102)
	at org.springframework.boot.context.config.ConfigDataLocationResolvers.resolve(ConfigDataLocationResolvers.java:94)
	at org.springframework.boot.context.config.ConfigDataImporter.resolve(ConfigDataImporter.java:106)
	at org.springframework.boot.context.config.ConfigDataImporter.resolve(ConfigDataImporter.java:98)
	at org.springframework.boot.context.config.ConfigDataImporter.resolveAndLoad(ConfigDataImporter.java:86)
	at org.springframework.boot.context.config.ConfigDataEnvironmentContributors.withProcessedImports(ConfigDataEnvironmentContributors.java:129)
	at org.springframework.boot.context.config.ConfigDataEnvironment.processInitial(ConfigDataEnvironment.java:245)
	at org.springframework.boot.context.config.ConfigDataEnvironment.processAndApply(ConfigDataEnvironment.java:232)
	at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:96)
	at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:89)
	at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEnvironmentPreparedEvent(EnvironmentPostProcessorApplicationListener.java:134)
	at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEvent(EnvironmentPostProcessorApplicationListener.java:117)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:185)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:178)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:156)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:138)
	at org.springframework.boot.context.event.EventPublishingRunListener.multicastInitialEvent(EventPublishingRunListener.java:136)
	at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:81)
	at org.springframework.boot.SpringApplicationRunListeners.lambda$environmentPrepared$2(SpringApplicationRunListeners.java:64)
	at java.base/java.lang.Iterable.forEach(Iterable.java:75)
	at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:118)
	at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:112)
	at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:63)
	at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:353)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:313)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1361)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1350)
	at com.att.training.springboot.examples.FeatureManagementApplication.main(FeatureManagementApplication.java:12)
Caused by: java.lang.IllegalStateException: File extension is not known to any PropertySourceLoader. If the location is meant to reference a directory, it must end in '/' or File.separator
	at org.springframework.boot.context.config.StandardConfigDataLocationResolver.getReferencesForFile(StandardConfigDataLocationResolver.java:235)
	at org.springframework.boot.context.config.StandardConfigDataLocationResolver.getReferences(StandardConfigDataLocationResolver.java:139)
	... 32 common frames omitted

To Reproduce
Set spring.cloud.azure.appconfiguration.enabled to false and either omit spring.cloud.azure.appconfiguration.stores[0].connection-string or set it to an empty string.

spring:
  config:
    import: azureAppConfiguration
  cloud:
    azure:
      appconfiguration:
        enabled: false
        stores:
        - connection-string: ""
          feature-flags:
            enabled: true
            selects:
            - label-filter: ',${spring.profiles.active}'
          monitoring:
            feature-flag-refresh-interval: 10s

Expected behavior
Connection string validation is skipped when spring.cloud.azure.appconfiguration.enabled is false

Setup:
OS: macOs 15.7.2
IDE: Intellij 2025.3.1
Library/Libraries: com.azure.spring:spring-cloud-azure-starter-appconfiguration-config:6.1.0
Java version: 21
Frameworks: Spring Boot 3.5.8

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[github-actions]

@moarychan @Netyyyy @rujche @saragluna

[github-actions]

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