Vault cluster 'tier' added as an optional input

[waxb]

🛠️ Description

Added tier as a required option for Vault clusters.
#143

🏗️ Acceptance tests

• Are there any feature flags that are required to use this functionality? no
• Have you added an acceptance test for the functionality being added?
• Have you run the acceptance tests on this branch?

Output from acceptance testing:

waxb@mbp:terraform-provider-hcp (vault-cluster-tier *)$ make testacc TESTARGS='-run=TestAccVaultCluster'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/... -v -run=TestAccVaultCluster -timeout 120m
?   	github.com/hashicorp/terraform-provider-hcp/internal/clients	[no test files]
testing: warning: no tests to run
PASS
ok  	github.com/hashicorp/terraform-provider-hcp/internal/consul	(cached) [no tests to run]
testing: warning: no tests to run
PASS
ok  	github.com/hashicorp/terraform-provider-hcp/internal/input	(cached) [no tests to run]
=== RUN   TestAccVaultClusterAdminToken
--- PASS: TestAccVaultClusterAdminToken (778.24s)
=== RUN   TestAccVaultCluster
--- PASS: TestAccVaultCluster (771.51s)
PASS
ok  	github.com/hashicorp/terraform-provider-hcp/internal/provider	1550.281s

Note: TestAccVaultClusterAdminToken tests for standard_small

[hashicorp-cla]

All committers have signed the CLA.

[bcmdarroch]

Hi @waxb! Thank you for this contribution 🎉

There's just a couple build issues that need fixing, and a few suggestions I left. Once you resolve those we can get this in!

[waxb]

Also I realised that the docu is autogenerated :-)

[bcmdarroch]

Excellent work on this! Thanks for your patience with my reviews! 🎉

Once merged, I should be able to cut a release in the next few days.

[waxb]

Thank you @nadilas for answering my funky golang questions!