Update workflow for changing RabbitMQ configuration

[tbroden84]

To be able to only change one or multiple configurations, without needing to add all to the configuration file.

Previous need to add all arguments to update configuration:

resource "cloudamqp_rabbitmq_configuration" "rabbit_config" {
  instance_id = cloudamqp_instance.instance.id
  channel_max = 0
  connection_max = -1
  consumer_timeout = -1
  heartbeat = 120
  log_exchange_level = "error"
  max_message_size = 134217728
  queue_index_embed_msgs_below = 4096
  vm_memory_high_watermark = 0.81
}

Change all arguments to also be computed, so each argument can be either used or left out in the providers configuration file.

• If used, the RabbitMQ configuration will be updated with the argument.
• Left out, argument will be read from the RabbitMQ configuration and populate the state file.

resource "cloudamqp_rabbitmq_configuration" "rabbit_config" {
  instance_id = cloudamqp_instance.instance.id
  consumer_timeout = -1
  heartbeat = 60
}

Next update:

resource "cloudamqp_rabbitmq_configuration" "rabbit_config" {
  instance_id = cloudamqp_instance.instance.id
  consumer_timeout = 10000
  heartbeat = 120
}