feat(tox): test pydantic v1 and v2

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 skipdist = true
-envlist = lint, static, unit, examples
+envlist = lint, static, unit, pydantic{1,2}-examples
 
 [testenv]
 allowlist_externals =
@@ -13,6 +13,11 @@ command =
     black src
     black tests
 	black examples
+usedevelop = false
+deps =
+    pydantic1: pydantic>=1.0,<2.0
+    pydantic2: pydantic>=2.0,<3.0
+    httpx>=0.27.0,<0.28.0
 
 [testenv:static]
 commands =
@@ -24,6 +29,6 @@ commands =
 commands =
 	pytest tests/unit -v {posargs}
 
-[testenv:examples]
+[testenv:pydantic{1,2}-examples]
 commands =
-	pytest examples -v {posargs}
+    pytest examples -v {posargs}