Fix empty data_json attribute

[ned1313]

Description

This PR updates the vault_kv_secret_v2 resource to correctly populate the data_json attribute.

The issue was readResp.Data which is a map[string]interface{} that contains the actual secret data, but the code was trying to marshal [data.Data] which is a [types.Map] (Terraform Framework type). Rather than throw an error, the resulting marshalled JSON was empty {}. The updated code marshals readResp.Data instead to populate the data_json attribute.

Closes #2520

Checklist

• Added CHANGELOG entry (only for user-facing changes)
• Acceptance tests where run against all supported Vault Versions

Output from acceptance testing:

$ TESTARGS="--run TestAccKVV2Secret" make testacc
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test --run TestAccKVV2Secret -timeout 30m ./...
?       github.com/hashicorp/terraform-provider-vault   [no test files]
?       github.com/hashicorp/terraform-provider-vault/cmd/coverage      [no test files]
?       github.com/hashicorp/terraform-provider-vault/cmd/generate      [no test files]
ok      github.com/hashicorp/terraform-provider-vault/codegen   (cached) [no tests to run]
?       github.com/hashicorp/terraform-provider-vault/helper    [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/consts   [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/framework/base[no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/framework/client       [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/framework/errutil      [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/framework/model[no test files]
ok      github.com/hashicorp/terraform-provider-vault/internal/framework/validators   (cached) [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/internal/identity/entity(cached) [no tests to run]
?       github.com/hashicorp/terraform-provider-vault/internal/identity/group[no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/identity/mfa  [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/pki      [no test files]
ok      github.com/hashicorp/terraform-provider-vault/internal/provider (cached) [no tests to run]
?       github.com/hashicorp/terraform-provider-vault/internal/provider/fwprovider    [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/providertest  [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/rotation [no test files]
?       github.com/hashicorp/terraform-provider-vault/internal/sync     [no test files]
ok      github.com/hashicorp/terraform-provider-vault/internal/vault/secrets/ephemeral        1.527s
ok      github.com/hashicorp/terraform-provider-vault/internal/vault/sys     (cached) [no tests to run]
?       github.com/hashicorp/terraform-provider-vault/schema    [no test files]
ok      github.com/hashicorp/terraform-provider-vault/testutil  (cached) [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/util      (cached) [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/util/mountutil    (cached) [no tests to run]
ok      github.com/hashicorp/terraform-provider-vault/vault     (cached) [no tests to run]
...

Community Note

• Please vote on this pull request by adding a 👍 reaction to the original pull request comment to help the community and maintainers prioritize this request
• Please do not leave "+1" comments, they generate extra noise for pull request followers and do not help prioritize the request

PCI review checklist

• I have documented a clear reason for, and description of, the change I am making.

• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.

• If applicable, I've documented the impact of any changes to security controls.

  Examples of changes to security controls include using new access control methods, adding or removing logging pipelines, etc.

[octo]

@kiannaquach I noticed this PR has been open for a while. My team recently encountered this exact bug, which caused significant debugging time for us. Since the fix appears straightforward, well-documented, and includes tests, I'm curious if there's anything specific holding up the review process or if there's any way I can help move this PR forward? We'd really appreciate having this resolved in an upcoming release.