DNS record name validation improvements

[janik-cloudflare]

• Rename validateRecordName to validateRecordContent to more accurately reflect its purpose (and update error messages).
• Add a validation to ensure that DNS record names are non-empty.

Closes #1621

[github-actions]

changelog detected ✅

[jacobbednarz]

acceptance tests are all passing

TF_ACC=1 go test $(go list ./...) -v -run "^TestAccCloudflareRecord_" -count 1 -parallel 1 -timeout 120m -parallel 1
?       github.com/cloudflare/terraform-provider-cloudflare     [no test files]
=== RUN   TestAccCloudflareRecord_Import
--- PASS: TestAccCloudflareRecord_Import (17.94s)
=== RUN   TestAccCloudflareRecord_Basic
=== PAUSE TestAccCloudflareRecord_Basic
=== RUN   TestAccCloudflareRecord_CaseInsensitive
=== PAUSE TestAccCloudflareRecord_CaseInsensitive
=== RUN   TestAccCloudflareRecord_Apex
=== PAUSE TestAccCloudflareRecord_Apex
=== RUN   TestAccCloudflareRecord_LOC
=== PAUSE TestAccCloudflareRecord_LOC
=== RUN   TestAccCloudflareRecord_SRV
=== PAUSE TestAccCloudflareRecord_SRV
=== RUN   TestAccCloudflareRecord_CAA
=== PAUSE TestAccCloudflareRecord_CAA
=== RUN   TestAccCloudflareRecord_Proxied
=== PAUSE TestAccCloudflareRecord_Proxied
=== RUN   TestAccCloudflareRecord_Updated
=== PAUSE TestAccCloudflareRecord_Updated
=== RUN   TestAccCloudflareRecord_typeForceNewRecord
=== PAUSE TestAccCloudflareRecord_typeForceNewRecord
=== RUN   TestAccCloudflareRecord_hostnameForceNewRecord
=== PAUSE TestAccCloudflareRecord_hostnameForceNewRecord
=== RUN   TestAccCloudflareRecord_CreateAfterManualDestroy
=== PAUSE TestAccCloudflareRecord_CreateAfterManualDestroy
=== RUN   TestAccCloudflareRecord_TtlValidation
=== PAUSE TestAccCloudflareRecord_TtlValidation
=== RUN   TestAccCloudflareRecord_ExplicitProxiedFalse
=== PAUSE TestAccCloudflareRecord_ExplicitProxiedFalse
=== RUN   TestAccCloudflareRecord_MXWithPriorityZero
=== PAUSE TestAccCloudflareRecord_MXWithPriorityZero
=== RUN   TestAccCloudflareRecord_TtlValidationUpdate
=== PAUSE TestAccCloudflareRecord_TtlValidationUpdate
=== CONT  TestAccCloudflareRecord_Basic
--- PASS: TestAccCloudflareRecord_Basic (10.95s)
=== CONT  TestAccCloudflareRecord_typeForceNewRecord
--- PASS: TestAccCloudflareRecord_typeForceNewRecord (18.90s)
=== CONT  TestAccCloudflareRecord_TtlValidationUpdate
--- PASS: TestAccCloudflareRecord_TtlValidationUpdate (12.96s)
=== CONT  TestAccCloudflareRecord_MXWithPriorityZero
--- PASS: TestAccCloudflareRecord_MXWithPriorityZero (8.39s)
=== CONT  TestAccCloudflareRecord_ExplicitProxiedFalse
--- PASS: TestAccCloudflareRecord_ExplicitProxiedFalse (20.36s)
=== CONT  TestAccCloudflareRecord_TtlValidation
--- PASS: TestAccCloudflareRecord_TtlValidation (3.63s)
=== CONT  TestAccCloudflareRecord_CreateAfterManualDestroy
--- PASS: TestAccCloudflareRecord_CreateAfterManualDestroy (15.76s)
=== CONT  TestAccCloudflareRecord_hostnameForceNewRecord
--- PASS: TestAccCloudflareRecord_hostnameForceNewRecord (17.70s)
=== CONT  TestAccCloudflareRecord_SRV
--- PASS: TestAccCloudflareRecord_SRV (8.70s)
=== CONT  TestAccCloudflareRecord_Updated
--- PASS: TestAccCloudflareRecord_Updated (17.75s)
=== CONT  TestAccCloudflareRecord_Proxied
--- PASS: TestAccCloudflareRecord_Proxied (9.85s)
=== CONT  TestAccCloudflareRecord_CAA
--- PASS: TestAccCloudflareRecord_CAA (15.10s)
=== CONT  TestAccCloudflareRecord_LOC
--- PASS: TestAccCloudflareRecord_LOC (9.10s)
=== CONT  TestAccCloudflareRecord_CaseInsensitive
--- PASS: TestAccCloudflareRecord_CaseInsensitive (12.45s)
=== CONT  TestAccCloudflareRecord_Apex
--- PASS: TestAccCloudflareRecord_Apex (8.60s)
PASS
ok      github.com/cloudflare/terraform-provider-cloudflare/internal/provider   208.651s
?       github.com/cloudflare/terraform-provider-cloudflare/tools/cmd/changelog-check   [no test files]
?       github.com/cloudflare/terraform-provider-cloudflare/tools/cmd/maintainer-only-file-check        [no test files]
?       github.com/cloudflare/terraform-provider-cloudflare/tools/cmd/tf-log-check      [no test files]
?       github.com/cloudflare/terraform-provider-cloudflare/version     [no test files]

[github-actions]

This functionality has been released in v3.19.0 of the Terraform Cloudflare Provider.

Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!