### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Sending a message with body:
`"&quot;&quot;"`
is received on the consumer side with body:
`""""`

### Expected Behavior

Sending a message with body:
"&quot;&quot;"
is received on the consumer side with body:
"&quot;&quot;"

### How are you starting LocalStack?

Custom (please describe below)

### Steps To Reproduce

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

Running localstack in docker desktop on Mac using helm chart

https://localstack.github.io/helm-charts
version 0.3.7
Image version: 0.14.3

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



### Environment

```markdown
- OS: macOS Monterey
- LocalStack: 0.14.3
```


### Anything else?

_No response_
 any param whose value is None.
            return
        member_shape = shape.member
        if shape.serialization.get("flattened"):
            # If sual name for the parent
            # element for the children.
            element_name = self._get_seriali
            list_node = xmlnode
        else:
            element_name = self._get_serialized_name(member_shape, "member")
            list_node = ETree.SubElement(xmlnode, name)
        for item in params:
            # Don't serialize any item which is None
            if item is not None:
                self._serialize(member_shape, item, list_node, element_name, mime_type)
    def _serialize_type_map(
        self, xmlnode: ETree.Element, params: dict, shape: MapShape, name: str, mime_type: str
    ) -> None:
        """
        Given the ``name`` of MyMap, an he ``flattened: False``
        we serialize this as:
          <MyMap>
            <entry>
              <key>key1</key>
              <value>val1</value>
            </entry>
            <entry>
              <key>key2</key>
              
            </entry>
          </MyMap>
        If it is flattened, it is serialized as follows:
          <MyMap>
            <key>key1</key>
            <value>val1</value>
          </MyMap>
          <MyMap>
            <key>key2</key>
            
          </MyMap>
        """
        if params is None:
            # Don't serialize a non-existing map
            return
        if shape.serialization.get("flattened"):
            entries_node = xmlnode
            entry_node_name = name
        else:
            entries_node = ETree.SubElement(xmlnode, name)
            entry_node_name = "entry"
        for key, value in params.items():
            if value is None:
                # Don't serialize any param whose value is None.
                continue
            entry_node = ETree.SubElement(entries_node, entry_node_name)
            key_name = self._get_serialized_name(shape.key, default_name="key")