Avoid storing sensitive keys in Angular applications as they are not securely stored and can be accessed publicly. The key you have is a publishable key meant for public access, not a secret key, so it should not be kept in Angular.
It seems like you are already taking the right approach with your comment response above.
Always keep your secrets in private API's and avoid publishing them to public repositories by hiding them in .gitignore. Utilizing Google Secret Manager is a good practice!
If someone were to obtain your pk_key, they would only be able to make requests using the secret key to hit your endpoint, although this scenario is unlikely. To prevent this, consider enabling CORS on your APIs to block unwanted web requests.
I recommend storing keys in the environment.ts file, as it is a common practice for several reasons. It allows for easy checking, updating, or deleting of keys. When setting up pipelines for different environments, this method makes it easier to manage and ensures smooth local development.