feat: Data object for Service properties

Dear implementers,
it appears to me that the Data object for the Services property is not correctly implemented (see https://cyclonedx.org/docs/1.6/json/#services_items_data).
I am trying to instantiate a Service, and upon populating the data property, I get this hint from the docs


The DataClassification class is defined as
```py
@serializable.serializable_class
class DataClassification:
"""
This is our internal representation of the `dataClassificationType` complex type within the CycloneDX standard.

DataClassification might be deprecated since CycloneDX 1.5, but it is not deprecated in this library.
In fact, this library will try to provide a compatibility layer if needed.

.. note::
See the CycloneDX Schema for dataClassificationType:
https://cyclonedx.org/docs/1.4/xml/#type_dataClassificationType
"""

def __init__(
self, *,
flow: DataFlow,
classification: str
) -> None:
self.flow = flow
self.classification = classification

@property
@serializable.xml_attribute()
def flow(self) -> DataFlow:
"""
Specifies the flow direction of the data.

Valid values are: inbound, outbound, bi-directional, and unknown.

Direction is relative to the service.

- Inbound flow states that data enters the service
- Outbound flow states that data leaves the service
- Bi-directional states that data flows both ways
- Unknown states that the direction is not known

Returns:
`DataFlow`
"""
return self._flow

@flow.setter
def flow(self, flow: DataFlow) -> None:
self._flow = flow

@property
@serializable.xml_name('.')
@serializable.xml_string(serializable.XmlStringSerializationType.NORMALIZED_STRING)
def classification(self) -> str:
"""
Data classification tags data according to its type, sensitivity, and value if altered, stolen, or destroyed.

Returns:
`str`
"""
return self._classification

@classification.setter
def classification(self, classification: str) -> None:
self._classification = classification

def __eq__(self, other: object) -> bool:
if isinstance(other, DataClassification):
return hash(other) == hash(self)
return False

def __lt__(self, other: object) -> bool:
if isinstance(other, DataClassification):
return _ComparableTuple((
self.flow, self.classification
)) < _ComparableTuple((
other.flow, other.classification
))
return NotImplemented

def __hash__(self) -> int:
return hash((self.flow, self.classification))

def __repr__(self) -> str:
return f''
```
Which seems to be missing the "source" and "destination" properties.

This my poetry.lock entry for cyclonedx-python-lib
```toml
name = "cyclonedx-python-lib"
version = "7.6.0"
description = "Python library for CycloneDX"
optional = false
python-versions = "<4.0,>=3.8"
files = [
{file = "cyclonedx_python_lib-7.6.0-py3-none-any.whl", hash = "sha256:30655e89e5f987dc8d57835919748d71589fafeb33ff1dec45048eb72eda3cf9"},
{file = "cyclonedx_python_lib-7.6.0.tar.gz", hash = "sha256:fa481d5f0d82728cb6a32e55f8ba9c666ba75a2bd99eb643228e3011c56bb5c4"},
]
```

Would it be possible for you to adjust this, or let me know what I could do otherwise? Thank you!