Refactor: cleanup usage of parseTwoPartID

[kpfleming]

This function is used in many resources to parse colon-separated
two-part identifier strings, and it emits an error message when
the string does not match the expected format. The error message
indicates that the format was expected to be "organization:name"
but this is only true for some resources, not all of them. As a
result users may get an error while attempting to import a resource
which gives them incorrect information about the identitier format.

This patch improves the function to accept a pair of label strings,
and it uses them when constructing the error message, so the message
will be tailored to the call site's desired format for the string.

Signed-off-by: Kevin P. Fleming kpfleming@bloomberg.net

[jcudit]

👍 on the tradeoff between end user experience and developer friction.

[jcudit]

This one triggered 3 failed tests:

------- Stdout: -------
=== RUN   TestAccGithubRepository_createFromTemplate
=== PAUSE TestAccGithubRepository_createFromTemplate
=== CONT  TestAccGithubRepository_createFromTemplate
--- FAIL: TestAccGithubRepository_createFromTemplate (4.26s)
    testing.go:569: Step 0 error: errors during apply:
        
        Error: Provider produced inconsistent result after apply
        
        When applying changes to github_repository.foo, provider "github" produced an
        unexpected new value for was present, but now absent.
        
        This is a bug in the provider, which should be reported in the provider's own
        issue tracker.
        
FAIL

------- Stdout: -------
=== RUN   TestAccGithubRepository_autoInitForceNew
=== PAUSE TestAccGithubRepository_autoInitForceNew
=== CONT  TestAccGithubRepository_autoInitForceNew
--- FAIL: TestAccGithubRepository_autoInitForceNew (17.41s)
    testing.go:630: Error destroying resource! WARNING: Dangling resources
        may exist. The full state and error is shown below.
        
        Error: errors during apply: DELETE https://api.github.com/repos/terraformtesting/tf-acc-test-6a4gmvihhb: 404 Not Found []
        
        State: github_repository.foo:
          ID = tf-acc-test-6a4gmvihhb
          provider = provider.github
          allow_merge_commit = true
          allow_rebase_merge = true
          allow_squash_merge = true
          archived = false
          auto_init = true
          default_branch = master
          description = 
          etag = W/"a75ede4cf216525f64e5ae4115e80931"
          full_name = terraformtesting/tf-acc-test-6a4gmvihhb
          git_clone_url = git://github.com/terraformtesting/tf-acc-test-6a4gmvihhb.git
          gitignore_template = Go
          has_downloads = false
          has_issues = false
          has_projects = false
          has_wiki = false
          homepage_url = 
          html_url = https://github.com/terraformtesting/tf-acc-test-6a4gmvihhb
          http_clone_url = https://github.com/terraformtesting/tf-acc-test-6a4gmvihhb.git
          license_template = mpl-2.0
          name = tf-acc-test-6a4gmvihhb
          private = false
          ssh_clone_url = git@github.com:terraformtesting/tf-acc-test-6a4gmvihhb.git
          svn_url = https://github.com/terraformtesting/tf-acc-test-6a4gmvihhb
          template.# = 0
FAIL

------- Stdout: -------
=== RUN   TestAccGithubRepositoryWebhook_basic
=== PAUSE TestAccGithubRepositoryWebhook_basic
=== CONT  TestAccGithubRepositoryWebhook_basic
--- FAIL: TestAccGithubRepositoryWebhook_basic (7.73s)
    testing.go:569: Step 1 error: errors during apply:
        
        Error: PATCH https://api.github.com/repos/terraformtesting/foo-1ywn3a3878/hooks/178788842: 404 Not Found []
        
          on /opt/teamcity-agent/temp/buildTmp/tf-test919770926/main.tf line 16:
          (source code not available)
        
        
FAIL

I've got this queued for investigation but looks more involved than the others.

[jcudit]

Hmm, I've run the tests locally instead of through CI and am seeing positive results. I feel confident in merging this change to unblock #318.