Add support for parsing of datetime type 79

The new year's eve of 2024 is from a real-world meter data, the other
test is from a KMP document (adjusted for the "number of bytes" and
"size and exponent" bytes).

Author: jktjkt

src/pykmp/constants.py

@@ -235,6 +235,7 @@
     64: "Datetime",
     65: "imp/l",
     66: "l/imp",
+    79: "DST YY-MM-DD hh:mm:ss",
     85: "%RH",
     86: "%O\N{SUBSCRIPT TWO}",
     87: "m/s",

src/pykmp/registers.py

@@ -59,6 +59,12 @@ def from_register_data(cls, reg: messages.RegisterData) -> Self:
                 # mm-dd
                 d = int.from_bytes(reg.value[2:], 'big')
                 value_str = f'{(d // 100 % 100):02}-{(d % 100):02}'
+            case 0x4f:
+                # DST yy:mm:dd hh:mm:ss
+                dst = reg.value[2]
+                value_str = f'{(2000 + reg.value[3]):02}-{reg.value[4]:02}-{reg.value[5]:02} ' \
+                    + f'{reg.value[6]:02}:{reg.value[7]:02}:{reg.value[8]:02}' \
+                    + f'{"+" if dst > 0 else "-"}{(dst // 60):02}:{(dst % 60):02}'
             case _:
                 value_dec = codec.FloatCodec.decode(reg.value)
         return cls(

tests/test_registers.py

@@ -52,6 +52,22 @@
             None,
             'mm:dd',
         ),
+        pytest.param(
+            348,
+            79,
+            '07 00 00 18 0c 1f 00 00 04',
+            '2024-12-31 00:00:04-00:00',
+            None,
+            'DST YY-MM-DD hh:mm:ss',
+        ),
+        pytest.param(
+            348,
+            79,
+            '07 00 3C 10 06 1E 0E 30 37',
+            '2016-06-30 14:48:55+01:00',
+            None,
+            'DST YY-MM-DD hh:mm:ss',
+        ),
     ]
 )
 def test_register_parsing(id_, unit, blob_with_size, value_str, value_dec, unit_str):