ts_31_102: EF_SUPI_NAI: Decode/Encode GLI+GCI as UTF-8 strings

According to TS 23.003 Section 28.15 and 28.16 both GLI and GCI
are NAI as defined in IETF RFC 7542, which in turn specifies they
are encoded in UTF-8.

Change-Id: I0a82bd0d0a2badd7bc4a1f8de2c3e3c144ee5b12

pySim/ts_31_102.py

@@ -1066,11 +1066,11 @@ class EF_SUPI_NAI(TransparentEF):
 
     class GlobalLineIdentifier(TLV_IE, tag=0x81):
         # TS 23.003 clause 28.16.2
-        pass
+        _construct = GreedyString("utf8")
 
     class GlobalCableIdentifier(TLV_IE, tag=0x82):
         # TS 23.003 clause 28.15.2
-        pass
+        _construct = GreedyString("utf8")
 
     class NAI_TLV_Collection(TLV_IE_Collection,
                              nested=[NetworkSpecificIdentifier, GlobalLineIdentifier, GlobalCableIdentifier]):