chore: Update charm libraries (#118)

lib/charms/tls_certificates_interface/v3/tls_certificates.py

@@ -312,7 +312,7 @@ def _on_all_certificates_invalidated(self, event: AllCertificatesInvalidatedEven
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 5
+LIBPATCH = 6
 
 PYDEPS = ["cryptography", "jsonschema"]
 
@@ -450,6 +450,10 @@ class ProviderCertificate:
     chain: List[str]
     revoked: bool
 
+    def chain_as_pem(self) -> str:
+        """Return full certificate chain as a PEM string."""
+        return "\n\n".join(reversed(self.chain))
+
 
 class CertificateAvailableEvent(EventBase):
     """Charm Event triggered when a TLS certificate is available."""
@@ -484,6 +488,10 @@ def restore(self, snapshot: dict):
         self.ca = snapshot["ca"]
         self.chain = snapshot["chain"]
 
+    def chain_as_pem(self) -> str:
+        """Return full certificate chain as a PEM string."""
+        return "\n\n".join(reversed(self.chain))
+
 
 class CertificateExpiringEvent(EventBase):
     """Charm Event triggered when a TLS certificate is almost expired."""