Document ZENML_ACTIVE_PROJECT_ID environment variable (#3992)

* Update documentation for environment variable usage

This commit enhances the documentation by clarifying the usage of the `ZENML_ACTIVE_PROJECT_ID` environment variable in the context of client configuration. It ensures users understand how to set their active project and the default project configuration effectively.

Additionally, it improves the formatting and consistency of the environment variable examples across the documentation.

* Add 403 exception handling for HF token link

Author: strickvl

docs/book/getting-started/zenml-pro/projects.md

@@ -45,6 +45,12 @@ This command sets the "default" project as your active project. All subsequent Z
 Best practice is to set your active project right after running `zenml init`, just like you would set an active stack. This ensures all your resources are properly organized within the project.
 {% endhint %}
 
+You can also set the project to be used by your client via an environment variable:
+
+```bash
+export ZENML_ACTIVE_PROJECT_ID=<PROJECT_ID>
+```
+
 ### Setting a default project
 
 The default project is something that each user can configure. This project will be automatically set as the active project when you connect your local Python client to a ZenML Pro workspace.

docs/book/reference/environment-variables.md

@@ -135,11 +135,12 @@ For more information on server configuration, see the [ZenML Server documentatio
 
 ## Client configuration
 
-Setting the `ZENML_STORE_URL` and `ZENML_STORE_API_KEY` environment variables automatically connects your ZenML Client to the specified server. This method is particularly useful when you are using the ZenML client in an automated CI/CD workload environment like GitHub Actions or GitLab CI or in a containerized environment like Docker or Kubernetes:
+Setting the `ZENML_STORE_URL`, `ZENML_STORE_API_KEY` and `ZENML_ACTIVE_PROJECT_ID` environment variables automatically connects your ZenML Client to the specified server for a specific project. This method is particularly useful when you are using the ZenML client in an automated CI/CD workload environment like GitHub Actions or GitLab CI or in a containerized environment like Docker or Kubernetes:
 
 ```bash
 export ZENML_STORE_URL=https://...
 export ZENML_STORE_API_KEY=<API_KEY>
+export ZENML_ACTIVE_PROJECT_ID=<PROJECT_ID>
 ```
 
 <figure><img src="https://static.scarf.sh/a.png?x-pxid=f0b4f458-0a54-4fcd-aa95-d5ee424815bc" alt="ZenML Scarf"><figcaption></figcaption></figure>

docs/link_checker.py

@@ -79,6 +79,32 @@
 except ImportError:
     HAS_REQUESTS = False
 
+# ------------------------------------------------------------------------------
+# Centralized exceptions for HTTP status codes we consider acceptable for
+# specific URLs or domains during link validation.
+#
+# How to extend:
+#   - To allow particular statuses for a *single* URL, add an entry to
+#     EXEMPT_URL_STATUS with the normalized URL (no trailing slash) and a set
+#     of allowed status codes.
+#   - To allow particular statuses for an entire *domain*, add an entry to
+#     EXEMPT_DOMAIN_STATUS with the domain suffix (e.g. "example.com") and a
+#     set of allowed status codes. Matching uses host.endswith(domain).
+# ------------------------------------------------------------------------------
+
+EXEMPT_URL_STATUS: Dict[str, set] = {
+    # Requires authentication; often returns 403 to unauthenticated HEAD/GET.
+    "https://huggingface.co/settings/tokens": {403},
+}
+
+EXEMPT_DOMAIN_STATUS: Dict[str, set] = {
+    # Some HashiCorp properties rate-limit automated checks.
+    "hashicorp.com": {429},
+    "developer.hashicorp.com": {429},
+    "terraform.io": {429},
+    "www.terraform.io": {429},
+}
+
 # Default policies for troublesome domains that frequently rate-limit automated traffic.
 # These defaults can be extended via CLI flags.
 DEFAULT_IGNORE_429_DOMAINS = {
@@ -96,6 +122,37 @@
 )
 
 
+def is_exception_status(cleaned_url: str, status_code: int) -> bool:
+    """
+    Return True if (cleaned_url, status_code) should be treated as valid based
+    on configured exemptions.
+
+    Rules:
+      - Exact-URL exemptions: compared after stripping any trailing slash.
+      - Domain exemptions: suffix match against the URL hostname.
+    """
+    if not cleaned_url.startswith(("http://", "https://")):
+        return False
+
+    # Exact URL exemptions (normalize by removing trailing slash)
+    normalized = cleaned_url.rstrip("/")
+    allowed = EXEMPT_URL_STATUS.get(normalized)
+    if allowed and status_code in allowed:
+        return True
+
+    # Domain exemptions
+    try:
+        host = urlparse(cleaned_url).hostname or ""
+    except Exception:
+        host = ""
+
+    for domain, codes in EXEMPT_DOMAIN_STATUS.items():
+        if host.endswith(domain) and status_code in codes:
+            return True
+
+    return False
+
+
 def find_markdown_files(directory: str) -> List[str]:
     """Find all markdown files in the given directory and its subdirectories."""
     markdown_files = []
@@ -334,7 +391,11 @@ def check_link_validity(
                 cleaned_url, timeout=timeout, allow_redirects=True
             )
 
-        # Soft-pass 429 for configured domains
+        # Check configured exception rules (domain- and URL-specific)
+        if is_exception_status(cleaned_url, response.status_code):
+            return (url, True, None, response.status_code)
+
+        # Also check for 429 soft-pass for configured domains (backward compatibility)
         if response.status_code == 429 and ignore_429:
             return (
                 url,