Timestamps are stored in the HLR DB in the new 'last_lu_seen' column
of the 'subscriber' table, in UTC and in granularity of seconds.
At present, osmo-hlr only records these timestamps but otherwise
makes no use of them. Because the timestamps are stored in a
human-readable form, they may already provide value to external
processes which need this information. For example:
sqlite> select imsi,last_lu_seen from subscriber;
901990000000001|2018-12-04 14:17:12
I didn't bother adding additional tests because the code added
with this commit is already being exercised by several calls
to db_subscr_lu() in db_test.c.
This change requires a HLR DB schema update. Existing databases
won't be upgraded automatically. However, osmo-hlr will refuse
to operate with databases which are not upgraded.
Change-Id: Ibeb49d45aec18451a260a6654b8c51b8fc3bec50
Related: OS#2838
638ba8cc04