### 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_
"""
    This Protocol allows proper typing for different kind of hash used by S3 (hashlib.shaX, zlib.crc32 from
    S3CRC32Checksum, and botocore CrtCrc32cChecksum).
    """
    def digest(self) -> bytes:
        ...
    def update(self, value: bytes):
        ...
def get_s3_checksum(algorithm) -> ChecksumHash:
    match algorithm:
        case ChecksumAlgorithm.CRC32:
            return S3CRC32Checksum()
        case ChecksumAlgorithm.CRC32C:
            from botocore.httpchecksum import CrtCrc32cChecksum
            return CrtCrc32cChecksum()
        case ChecksumAlgorithm.SHA1:
            return hashlib.sha1(usedforsecurity=False)
        case ChecksumAlgorithm.SHA256:
            return hashlib.sha256(usedforsecurity=False)
        case _:
            
            raise InvalidRequest("The value specified in the x-amz-trailer header is not supported")
class S3CRC32Checksum:
    """Implements a unified way of using zlib.crc32 compatibl with hashlib.sha and botocore CrtCrc32cChecksum"""
    __slots__ = ["checksum"]
    def __init__(self):
        self.checksum = None
    def update(self, value: bytes):