feat: build input features

pkg/ussdgw/conf/ussd.conf

@@ -0,0 +1,16 @@
+#HLR USSD Conf File
+
+
+[HLR USSDC]
+Format String="*C3B*S#"  //regular expression
+
+
+[UG-CSI]
+#ID  srvCode    gsmSCFAddr
+0    222        9186755920019EEEEE
+1    23        9186755920019EEEEE
+2    34        9186755920019EEEEE
+3    45        9186755920019EEEEE
+
+[USSD EAE]//service number < 9 digits service code <= 4 digits
+ID  SRVNum      ServiceCode