Cache github user id in memory (bazelbuild#4236)

Following up
bazelbuild#4191

This is to prevent the risk of hitting github api limit in presubmit.

Author: meteorcloudy

tools/bcr_validation.py

@@ -83,6 +83,9 @@ class BcrValidationResult(Enum):
 
 GITHUB_REPO_RE = re.compile(r"^(https://github.com/|github:)([^/]+/[^/]+)$")
 
+# Global cache for GitHub user IDs
+GITHUB_USER_ID_CACHE = {}
+
 
 def print_collapsed_group(name):
     print("\n\n--- {0}\n\n".format(name))
@@ -210,22 +213,27 @@ def check_github_url(repo_path, source_url):
 
 def get_github_user_id(github_username):
     """
-    Get the GitHub user ID for a given GitHub username.
+    Get the GitHub user ID for a given GitHub username, with caching.
 
     Args:
         github_username: The GitHub username to look up.
 
     Returns:
         The GitHub user ID if found, otherwise None.
     """
+    if github_username in GITHUB_USER_ID_CACHE:
+        return GITHUB_USER_ID_CACHE[github_username]
+
     url = f"https://api.github.com/users/{github_username}"
     headers = {}
     github_token = os.getenv("GITHUB_TOKEN")
     if github_token:
         headers["Authorization"] = f"token {github_token}"
     response = requests.get(url, headers=headers)
     if response.status_code == 200:
-        return response.json().get("id")
+        user_id = response.json().get("id")
+        GITHUB_USER_ID_CACHE[github_username] = user_id
+        return user_id
     return None