SecretManager Secret: Prevent recreation for "automatic" to "auto"

[c2thorn]

fixes hashicorp/terraform-provider-google#15885

Creates a custom diff that prevents immutability when following upgrade guide steps for replication.auto
Things to note:

• Does not prevent the reverse: removing "auto" and adding "automatic"
• Updating to an empty auto {} still calls the API with a trivial PATCH request.

Tested manually with local provider.

Release Note Template for Downstream PRs (will be copied)

secretmanager: fixed an issue in `google_secretmanager_secret` where replacing `replication.automatic` with `replication.auto` would destroy and recreate the resource

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 1 file changed, 32 insertions(+), 2 deletions(-))
Terraform Beta: Diff ( 1 file changed, 32 insertions(+), 2 deletions(-))
TF Conversion: Diff ( 1 file changed, 29 insertions(+))

[modular-magician]

Tests analytics

Total tests: 3075
Passed tests 2772
Skipped tests: 299
Affected tests: 4

Action taken

Found 4 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

TestAccBigtableAppProfile_bigtableAppProfileSingleclusterExample|TestAccBigtableAppProfile_bigtableAppProfileAnyclusterExample|TestAccBigtableAppProfile_bigtableAppProfileMulticlusterExample|TestAccSecretManagerSecret_automaticCmekUpdate

Get to know how VCR tests work

[modular-magician]

$\textcolor{green}{\textsf{Tests passed during RECORDING mode:}}$
TestAccBigtableAppProfile_bigtableAppProfileSingleclusterExample[Debug log]
TestAccBigtableAppProfile_bigtableAppProfileAnyclusterExample[Debug log]
TestAccBigtableAppProfile_bigtableAppProfileMulticlusterExample[Debug log]
TestAccSecretManagerSecret_automaticCmekUpdate[Debug log]

Rerun these tests in REPLAYING mode to catch issues

$\textcolor{green}{\textsf{No issues found for passed tests after REPLAYING rerun.}}$

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$\textcolor{green}{\textsf{All tests passed!}}$
View the build log or the debug log for each test