Render environment variables in kafka resource properties file

[aakashnand]

When I was trying to configure SASL settings for Kafka Connector, I tried using secrets https://trino.io/docs/current/security/secrets.html explained here. but the environment variables are not loaded in kafka-config.properties

Here are the settings I used

kafka_catalog.properties

connector.name=kafka
kafka.nodes=<BOOTSTRAP_SERVERS>
kafka.table-names=my-topic
kafka.hide-internal-columns=false
kafka.config.resources=/etc/trino/kafka-configuration.properties

kafka-configuration.properties

security.protocol=SASL_SSL
ssl.endpoint.identification.algorithm=
ssl.truststore.location=/etc/trino/kafka-trustore.jks
ssl.truststore.password=${ENV:KAFKA_TRUSTORE_PASS}

Apparently these values are showing following NULL error

Caused by: java.lang.IllegalArgumentException: Value not specified for key 'null' in JAAS config
	at org.apache.kafka.common.security.JaasConfig.parseAppConfigurationEntry(JaasConfig.java:116)
	at org.apache.kafka.common.security.JaasConfig.<init>(JaasConfig.java:63)
	at org.apache.kafka.common.security.JaasContext.load(JaasContext.java:90)
	at org.apache.kafka.common.security.JaasContext.loadClientContext(JaasContext.java:84)
	at org.apache.kafka.common.network.ChannelBuilders.create(ChannelBuilders.java:124)
	at org.apache.kafka.common.network.ChannelBuilders.clientChannelBuilder(ChannelBuilders.java:67)
	at org.apache.kafka.clients.ClientUtils.createChannelBuilder(ClientUtils.java:99)
	at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:741)

Additional Point:

• If we could extend this to properties file we should try to extend it to .xml file which can be useful for hive.config.resources

[aakashnand]

We should also update the document clarifying that secret may not work for some files on that line

[hashhar]

We're basically missing Bootstrap since we just call Properties#readProperties on whatever path is returned by KafkaConfig#getResourceConfigFiles.

BTW this is one of the downsides of such "escape hatches" provided by ability to passthrough arbitrary configs instead of building dedicated handling for a feature.

cc: @kokosing