change artifact name regex (#398)

~Having an issue with tests, but opening this for discussion in the
meantime.~

The PR adds support for uppercase letters and `_`. I decided against
support for `.` because there are some restrictions around how it can be
used in [git refs](https://git-scm.com/docs/git-check-ref-format).

Related: iterative/dvc#9821

TODO:
- [x] Tests
- [ ] DVC PR
- [ ] DVCLive PR to improve
[warning](https://github.com/iterative/dvclive/blob/95000f45638d5126b7d76833050f549167a7449d/src/dvclive/live.py#L462-L466)
- [ ] Docs PR

gto/constants.py

@@ -42,7 +42,7 @@ def tag_to_name(value):
 
 
 dirname = "[a-z0-9-_./]+"  # improve?
-name = r"[a-z0-9]([a-z0-9-/]*[a-z0-9])?"
+name = r"[a-z0-9]([a-z0-9-/_]*[A-Za-z0-9])?"
 semver = r"(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?"
 counter = "?P<counter>[0-9]+"
 name_re = re.compile(f"^{name}$")

tests/test_constants.py

@@ -17,6 +17,7 @@
         "1nn",
         "model-prod",
         "model-prod-v1",
+        "model_prod_v1",
         "dvclive/model",
     ],
 )
@@ -33,12 +34,13 @@ def test_check_name_is_valid(name):
         "###",
         "@@@",
         "a model",
-        "a_model",
+        "_model",
         "-model",
         "model-",
         "model@1",
         "model#1",
         "@namespace/model",
+        "DVCLive/Model",
     ],
 )
 def test_check_name_is_invalid(name):