Add script that generates a certificate with unlimited expiredate

Primary use is to generate default HTTPS certificate.

Sample usage:
/bin/gencert --country SE --state Vastmanland --city Vasteras --organisation ACME --organisation-unit Second  --common-name switch.local --out-certificate /tmp/out.cert --out-key /tmp/out.key

board/common/rootfs/bin/gencert

@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+# Generate a self signed certificate with unlimited expire time
+
+import argparse
+
+from cryptography import x509
+from cryptography.x509.oid import NameOID
+from cryptography.hazmat.primitives import hashes, serialization
+from cryptography.hazmat.primitives.asymmetric import rsa
+from cryptography.hazmat.backends import default_backend
+from datetime import datetime, timedelta
+
+# Generate private key
+private_key = rsa.generate_private_key(
+    public_exponent=65537,
+    key_size=2048,
+    backend=default_backend()
+
+)
+
+parser = argparse.ArgumentParser(description="Generate a self signed certificate")
+parser.add_argument('--country', required=True, help="Set country")
+parser.add_argument('--state', required=True, help="Set state or province name")
+parser.add_argument('--city', required=True, help="Set city name")
+parser.add_argument('--organisation', required=True, help="Set organisation name")
+parser.add_argument('--organisation-unit', required=True, help="Set organisation unit name")
+parser.add_argument('--common-name', required=True, help="Set common name")
+parser.add_argument('--out-certificate', required=True, help="Output certificate")
+parser.add_argument('--out-key', required=True, help="Output key")
+
+args = parser.parse_args()
+
+ # Builder for certificate
+subject = issuer = x509.Name([
+    x509.NameAttribute(NameOID.COUNTRY_NAME, args.country),
+    x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, args.state),
+    x509.NameAttribute(NameOID.LOCALITY_NAME, args.city),
+    x509.NameAttribute(NameOID.ORGANIZATION_NAME, args.organisation),
+    x509.NameAttribute(NameOID.ORGANIZATIONAL_UNIT_NAME, args.organisation_unit),
+    x509.NameAttribute(NameOID.COMMON_NAME, args.common_name),
+])
+certificate = x509.CertificateBuilder().subject_name(
+    subject
+).issuer_name(
+    issuer
+).public_key(
+    private_key.public_key()
+).serial_number(
+    x509.random_serial_number()
+).not_valid_before(
+    datetime(2000, 1, 1)
+).not_valid_after(
+    datetime(9999, 1, 1)
+).add_extension(
+    x509.SubjectAlternativeName([x509.DNSName(args.common_name)]),
+    critical=False,
+).sign(private_key, hashes.SHA256(), default_backend())
+
+# Serialize certificate and private key
+with open(args.out_certificate, "wb") as f:
+    f.write(certificate.public_bytes(serialization.Encoding.PEM))
+with open(args.out_key, "wb") as f:
+    f.write(private_key.private_bytes(
+        encoding=serialization.Encoding.PEM,
+        format=serialization.PrivateFormat.PKCS8,
+        encryption_algorithm=serialization.NoEncryption()
+    ))