Loosen up regex requirements in resolve single

OmegaConf's templating language allows very few characters.
There are some use cases where you'd want to have special characters
so that your custom resolver can handle resolution there (kind of like
embedding a templating language inside of OmegaConfs). This allows
such behaviour without seemingly breaking anything too majorly

omegaconf/config.py

@@ -416,7 +416,7 @@ def _resolve_value(root_node, inter_type, inter_key):
         return ret
 
     def _resolve_single(self, value):
-        match_list = list(re.finditer(r"\${(\w+:)?([\w\.%_-]+?)}", value))
+        match_list = list(re.finditer(r"\${(\w+:)?(.+?)}", value))
         if len(match_list) == 0:
             return value
 

tests/test_interpolation.py

@@ -250,6 +250,30 @@ def test_resolver_cache_2():
         OmegaConf.clear_resolvers()
 
 
+def test_resolver_that_allows_any_char():
+    def env_or_default(x):
+        split = x.split(",")
+        if len(split) > 1:
+            return os.getenv(split[0], split[1])
+        return os.getenv(split[0])
+
+    try:
+        OmegaConf.register_resolver("env_or_default", env_or_default)
+        os.environ["ENV_DEFAULT"] = "World"
+        c = OmegaConf.create(
+            dict(
+                default_env_set="${env_or_default:ENV_DEFAULT,no_world}",
+                default_env_unset="${env_or_default:NO_ENV_DEFAULT,World}",
+            )
+        )
+
+        assert c.default_env_set == "World"
+        assert c.default_env_unset == "World"
+    finally:
+        del os.environ['ENV_DEFAULT']
+        OmegaConf.clear_resolvers
+
+
 def test_copy_cache():
     OmegaConf.register_resolver("random", lambda _: random.randint(0, 10000000))
     c1 = OmegaConf.create(dict(