fix: Updating the documentation and adding tests for project length (#4628)

Updated the documentation to make it clear after spending some time.
 Addressing the issue - #4626

Signed-off-by: lrangine <19699092+lokeshrangineni@users.noreply.github.com>

Author: lokeshrangineni

sdk/python/feast/repo_config.py

@@ -158,9 +158,9 @@ class RepoConfig(FeastBaseModel):
     """Repo config. Typically loaded from `feature_store.yaml`"""
 
     project: StrictStr
-    """ str: Feast project id. This can be any alphanumeric string up to 16 characters.
+    """ str: This acts as a Feast unique project identifier. This can be any alphanumeric string and can have '_' but can not start with '_'.
         You can have multiple independent feature repositories deployed to the same cloud
-        provider account, as long as they have different project ids.
+        provider account, as long as they have different project identifier.
     """
 
     provider: StrictStr = "local"

sdk/python/tests/unit/sdk/python/feast/test_repo_operations_validate_feast_project_name.py

@@ -0,0 +1,26 @@
+from sdk.python.feast.repo_operations import is_valid_name
+
+
+def test_is_valid_name():
+    test_cases = [
+        # Valid project name cases
+        ("valid_name1", True),
+        ("username_1234", True),
+        ("valid123", True),
+        ("1234567890123456", True),
+        ("invalid_name_", True),
+        ("12345678901234567", True),
+        ("too_long_name_123", True),
+        # Invalid project name cases
+        ("_invalidName", False),
+        ("invalid-Name", False),
+        ("invalid name", False),
+        ("invalid@name", False),
+        ("invalid$name", False),
+        ("__", False),
+    ]
+
+    for name, expected in test_cases:
+        assert (
+            is_valid_name(name) == expected
+        ), f"Failed for project invalid name: {name}"