feat: add ibm_event_streams_schema_global_rule

[kccox]

What has been done?

Add a data source and resource for the IBM Event Streams schema-registry global compatibility rule.

• This is a configuration property of the schema registry, so always exists.
• The terraform create operation is the same as an update; the delete operation resets the rule to the default value.

The data model used by both data source and resource is:

• resource_instance_id: The CRN of the Event Streams service instance. (Our existing models for topics and schemas also use this to identify the service instance.) Required in data source and resource.
• config: The value of the rule. Computed in data source, required in resource.

The implementations use the Event Streams SDK client for our schema-registry API.

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Closes internal Event Streams feature request from BNPP.

Output from acceptance testing:

$ make testacc TEST=./ibm/service/eventstreams TESTARGS='-run=TestAccIBMEventStreamsSchemaGlobalCompatibilityRuleDataSource\|TestAccIBMEventStreamsSchemaGlobalCompatibilityRuleResource'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./ibm/service/eventstreams -v -run=TestAccIBMEventStreamsSchemaGlobalCompatibilityRuleDataSource\|TestAccIBMEventStreamsSchemaGlobalCompatibilityRuleResource -timeout 700m
  (skipping many warnings to set environment variables not used by this test)
=== RUN   TestAccIBMEventStreamsSchemaGlobalCompatibilityRuleDataSource
--- PASS: TestAccIBMEventStreamsSchemaGlobalCompatibilityRuleDataSource (30.54s)
=== RUN   TestAccIBMEventStreamsSchemaGlobalCompatibilityRuleResource
--- PASS: TestAccIBMEventStreamsSchemaGlobalCompatibilityRuleResource (39.46s)
PASS
ok  	github.com/IBM-Cloud/terraform-provider-ibm/ibm/service/eventstreams

[hkantare]

Why we are appending empty string

[kccox]

Our convention in Event Streams is that the first 8 fields of the CRN identify the service-instance, and the last two identify the resource on the instance. crnSegment[8] is the type of the resource, and crnSegment[9] is the identifier for the resource.

The type for the global rule is schema-global-compatibility-rule. Since the global compatibility rule is global, there is only one instance, so it does not have a unique identifier field. So we set segment 9 to "".

Example:

• input instanceCRN is crn:v1:staging:public:messagehub-vnext-integration:eu-gb:a/6db1b0d0b5c54ee5c201552547febcd8:4088c6f5-6a6b-49e8-a31d-712f09f23058::
• global rule CRN will be crn:v1:staging:public:messagehub-vnext-integration:eu-gb:a/6db1b0d0b5c54ee5c201552547febcd8:4088c6f5-6a6b-49e8-a31d-712f09f23058:schema-global-compatibility-rule:

In practice, the split segment 9 should already be "" since it should be coming from a service-instance CRN, in which the last two fields are not set. Setting it to "" is a precaution in case some other value was provided.