### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

- Localstack fails with HTTP 500, error code "InternalError", message "not enough values to unpack (expected 2, got 1)" when `CopySource` is an invalid string for `copy_object` API.

### Expected Behavior

- For the same API `copy_object`, the cloud fails with HTTP 400, error code "InvalidArgument".
- Localstack should handle invalid `CopySource` i.e., it is a dictionary with one value or an invalid string not adhering to "{bucket}/{key}" format.

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    botoclient.copy_object(CopySource="Invalid_random_string", Bucket="test_bucket", Key=key) 


 test_bucket is a valid bucket.  

### Environment

```markdown
- OS: Ubuntu 22.04.2 LTS
- LocalStack: 2.1.0
- boto3: 1.28.6
```


### Anything else?

_No response_
See https://docs.aws.amazon.com/AmazonS3/latest/userguide/acl-overview.html#canned-acl
    :param canned_acl: an S3 CannedACL
    :param owner: the current owner of the bucket or object
    :return: an AccessControlPolicy containing the Grants and Owner
    """
    owner_grantee = Grantee(**owner, Type=GranteeType.CanonicalUser)
    grants = [Grant(Grantee=owner_grantee, Permission=Permission.FULL_CONTROL)]
    match canned_acl:
        case ObjectCannedACL.private:
            pass  
        case ObjectCannedACL.public_read:
            grants.append(Grant(Grantee=ALL_USERS_ACL_GRANTEE, Permission=Permission.READ))
        case ObjectCannedACL.public_read_write:
            grants.append(Grant(Grantee=ALL_USERS_ACL_GRANTEE, Permission=Permission.READ))
            grants.append(Grant(Grantee=ALL_USERS_ACL_GRANTEE, Permission=Permission.WRITE))
        case ObjectCannedACL.authenticated_read:
            grants.append(
                Grant(Grantee=AUTHENTICATED_USERS_ACL_GRANTEE, Permission=Permission.READ)
            )
        case ObjectCannedACL.bucket_owner_read:
            pass  
        case ObjectCannedACL.bucket_owner_full_control:
            pass  
        case ObjectCannedACL.aws_exec_read:
            pass  
        case BucketCannedACL.log_delivery_write:
            grants.append(Grant(Grantee=LOG_DELIVERY_ACL_GRANTEE, Permission=Permission.READ_ACP))
            grants.append(Grant(Grantee=LOG_DELIVERY_ACL_GRANTEE, Permission=Permission.WRITE))
    return AccessControlPolicy(Owner=owner, Grants=grants)
def create_redirect_for_post_request(