Quantize all timestamps stored in the db

Fixes issue #1.
4 jobs for master in 5 minutes and 48 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build Pkgsrc
passed #7198
build_pkgsrc:stretch

00:00:21

 
  Build Pkg
failed #7199
amd64
build_pkg:stretch:amd64

00:01:03

failed #7200
arm64
build_pkg:stretch:arm64

00:05:26

 
  Upload Pkg
skipped #7201
upload_pkg
 
Name Stage Failure
failed
build_pkg:stretch:arm64 Build Pkg
?   	git.autistici.org/id/usermetadb/migrations	[no test files]
dh_auto_test: go test -v -p 4 git.autistici.org/id/usermetadb git.autistici.org/id/usermetadb/client git.autistici.org/id/usermetadb/cmd/user-meta-server git.autistici.org/id/usermetadb/migrations git.autistici.org/id/usermetadb/server returned exit code 1
debian/rules:8: recipe for target 'build' failed
make: *** [build] Error 1
dpkg-buildpackage: error: debian/rules build gave error exit status 2
debuild: fatal error at line 1116:
dpkg-buildpackage -rfakeroot -us -uc -b failed
ERROR: debuild failed!
ERROR: Job failed: exit code 1
failed
build_pkg:stretch:amd64 Build Pkg
?   	git.autistici.org/id/usermetadb/migrations	[no test files]
dh_auto_test: go test -v -p 2 git.autistici.org/id/usermetadb git.autistici.org/id/usermetadb/client git.autistici.org/id/usermetadb/cmd/user-meta-server git.autistici.org/id/usermetadb/migrations git.autistici.org/id/usermetadb/server returned exit code 1
debian/rules:8: recipe for target 'build' failed
make: *** [build] Error 1
dpkg-buildpackage: error: debian/rules build gave error exit status 2
debuild: fatal error at line 1116:
dpkg-buildpackage -rfakeroot -us -uc -b failed
ERROR: debuild failed!
ERROR: Job failed: exit code 1