Use a custom user agent when issuing HTTP requests. (#43)

# Description

This PR introduces adds a `User-Agent` header to `HTTP` requests made
from the API clients, this will allow us to identify which requests
originate from the SDK.

The `User-Agent` follows the format defined
[here](https://www.rfc-editor.org/rfc/rfc9110.html#name-user-agent).

This PR doesn't have `GDPR` implications as there's no personal data
used and the user agent cannot be used to identify a specific user or
clusters of users.

# References

- https://www.rfc-editor.org/rfc/rfc9110.html#name-user-agent
-
https://www.python-httpx.org/advanced/clients/#sharing-configuration-across-requests
-
https://www.python-httpx.org/advanced/clients/#merging-of-configuration

src/enlyze/api_clients/base.py

@@ -8,10 +8,20 @@
 import httpx
 from pydantic import BaseModel, ValidationError
 
+from enlyze._version import VERSION
 from enlyze.auth import TokenAuth
-from enlyze.constants import HTTPX_TIMEOUT
+from enlyze.constants import HTTPX_TIMEOUT, USER_AGENT
 from enlyze.errors import EnlyzeError, InvalidTokenError
 
+USER_AGENT_NAME_VERSION_SEPARATOR = "/"
+
+
+@cache
+def _construct_user_agent(
+    *, user_agent: str = USER_AGENT, version: str = VERSION
+) -> str:
+    return f"{user_agent}{USER_AGENT_NAME_VERSION_SEPARATOR}{version}"
+
 
 class ApiBaseModel(BaseModel):
     """Base class for ENLYZE platform API object models using pydantic
@@ -60,6 +70,7 @@ def __init__(
             auth=TokenAuth(token),
             base_url=httpx.URL(base_url),
             timeout=timeout,
+            headers={"user-agent": _construct_user_agent()},
         )
 
     @cache

src/enlyze/constants.py

@@ -22,3 +22,6 @@
 #: The maximum number of variables that can be used in a single request when querying
 #: timeseries data.
 MAXIMUM_NUMBER_OF_VARIABLES_PER_TIMESERIES_REQUEST = 100
+
+#: The user agent that the SDK identifies itself as when making HTTP requests
+USER_AGENT = "enlyze-python"

tests/enlyze/api_clients/test_base.py

@@ -7,11 +7,15 @@
 from hypothesis import HealthCheck, given, settings
 from hypothesis import strategies as st
 
+from enlyze._version import VERSION
 from enlyze.api_clients.base import (
+    USER_AGENT_NAME_VERSION_SEPARATOR,
     ApiBaseClient,
     ApiBaseModel,
     PaginatedResponseBaseModel,
+    _construct_user_agent,
 )
+from enlyze.constants import USER_AGENT
 from enlyze.errors import EnlyzeError, InvalidTokenError
 
 
@@ -83,6 +87,46 @@ def base_client(auth_token, string_model, base_url):
         yield client
 
 
+@pytest.fixture
+def custom_user_agent():
+    return "custom-user-agent"
+
+
+@pytest.fixture
+def custom_user_agent_version():
+    return "3.4.5"
+
+
+class TestConstructUserAgent:
+    def test__construct_user_agent_with_defaults(self):
+        ua, version = _construct_user_agent().split(USER_AGENT_NAME_VERSION_SEPARATOR)
+        assert ua == USER_AGENT
+        assert version == VERSION
+
+    def test__construct_user_agent_custom_agent(self, custom_user_agent):
+        ua, version = _construct_user_agent(user_agent=custom_user_agent).split(
+            USER_AGENT_NAME_VERSION_SEPARATOR
+        )
+        assert ua == custom_user_agent
+        assert version == VERSION
+
+    def test__construct_user_agent_custom_version(self, custom_user_agent_version):
+        ua, version = _construct_user_agent(version=custom_user_agent_version).split(
+            USER_AGENT_NAME_VERSION_SEPARATOR
+        )
+        assert ua == USER_AGENT
+        assert version == custom_user_agent_version
+
+    def test__construct_user_agent_custom_agent_and_version(
+        self, custom_user_agent, custom_user_agent_version
+    ):
+        ua, version = _construct_user_agent(
+            user_agent=custom_user_agent, version=custom_user_agent_version
+        ).split(USER_AGENT_NAME_VERSION_SEPARATOR)
+        assert ua == custom_user_agent
+        assert version == custom_user_agent_version
+
+
 @settings(suppress_health_check=[HealthCheck.function_scoped_fixture])
 @given(
     token=st.text(string.printable, min_size=1),