Support detecting Kafka by analyzing pom.xml and application.yml

[haoozhang]

Feature:

• Support detecting Kafka dependency by analyzing pom.xml and application.yaml
• Sample project Spring-Cloud-Stream-Kafka-Application can be used for azd init and azd up.

Fix:

• Removed connection string configuration when using MI auth, vice versa.
  Because when using MI, it still firstly try to get connection string (empty string), and failed to parse.
• Small fix for connection string configuration: SPRING_CLOUD_AZURE_EVENTHUBS_CONNECTIONSTRING -> SPRING_CLOUD_AZURE_EVENTHUBS_CONNECTION_STRING.
• Lowercase Env Var to avoid parsing confusion.

Open issue:

• When user has already specified connection string in project application.yaml, but selected the MI auth when azd init, we will inject the MI configuration and set the connection string as empty string explicitly. In this case, the configuration does NOT make app running.
  The root cause is that the empty connection string configuration is also be parsed by azure java SDK, created an issue to track: [BUG] Still use connection string auth even if the connection string property is set as empty string Azure/azure-sdk-for-java#42880

TODO:

• Better to detect the existing EventHub resource configuration in application.yaml, instead of always creating a new one.

[rujche]

@haoozhang

Removed connection string configuration when using MI auth, vice versa.

I kept the empty value to override the value in application.yml

Because when using MI, it still firstly try to get connection string (empty string), and failed to parse.

Are you sure the empty string will make the app start failed? I remember it work well when I test event hubs with mi set and connect string set to empty string.

[rujche]

@haoozhang

Small fix for connection string configuration: SPRING_CLOUD_AZURE_EVENTHUBS_CONNECTIONSTRING -> SPRING_CLOUD_AZURE_EVENTHUBS_CONNECTION_STRING.

Please read this: https://github.com/azure-javaee/azure-dev/wiki/Knowledge-Sharing#2-sometimes-the-environment-variable-not-take-effect-in-spring-boot-application

[rujche]

@haoozhang

When user has already specified auth (connection string / MI), but selected the different one when azd init (we will inject the configuration for application), maybe this inconsistent configuration does NOT make app running.
For example, user specified connection string auth in application.yaml, but select to use MI during azd init, then we will inject the MI config in bicep file. During the application starts up, it first get the connection string and use it to auth, but it's for the existing resource for now (not the new created one), then in this case, it fails to run.

Override these properties by environment variable can solve this problem.