(3/N) db_metadata_nexus database queries (validate schema, access)

Author: smklein

dev-tools/reconfigurator-cli/tests/output/cmds-target-release-stdout

@@ -1666,6 +1666,7 @@ to:   blueprint b82656b0-a9be-433d-83d0-e2bdf371777a
     internal DNS version:::   1 (unchanged)
     external DNS version:::   1 (unchanged)
     target release min gen:   1 (unchanged)
+    nexus gen::::::::::::::   1 (unchanged)
 
  OXIMETER SETTINGS:
     generation:   1 (unchanged)
@@ -1736,6 +1737,7 @@ to:   blueprint 31c84831-be52-4630-bc3f-128d72cd8f22
     internal DNS version:::   1 (unchanged)
     external DNS version:::   1 (unchanged)
     target release min gen:   1 (unchanged)
+    nexus gen::::::::::::::   1 (unchanged)
 
  OXIMETER SETTINGS:
     generation:   1 (unchanged)
@@ -1804,6 +1806,7 @@ to:   blueprint 778e3f3a-58b1-4a5e-acff-d23c5d7124c2
     internal DNS version:::   1 (unchanged)
     external DNS version:::   1 (unchanged)
     target release min gen:   1 (unchanged)
+    nexus gen::::::::::::::   1 (unchanged)
 
  OXIMETER SETTINGS:
     generation:   1 (unchanged)