Store lint warnings in the database

This commit adds the relevant tables and code to store lint warnings in the
database.

Currently, only lint checkers which don't require access to the network will
be run, as this allows the processing to happen without network access. Also,
this functionality won't work in older versions of Guix which don't expose the
lint warnings in a compatible way.

tests/model-lint-warning-message.scm

@@ -0,0 +1,57 @@
+(define-module (tests model-lint-warning-message)
+  #:use-module (srfi srfi-64)
+  #:use-module (ice-9 match)
+  #:use-module (guix-data-service database)
+  #:use-module (guix-data-service model lint-warning-message))
+
+(test-begin "test-model-lint-warning-message")
+
+(define data
+  '(("en" . "Test message")
+    ("es" . "Test message in Spanish")))
+
+(with-postgresql-connection
+ "test-model-lint-checker"
+ (lambda (conn)
+   (test-assert "single insert"
+     (with-postgresql-transaction
+      conn
+      (lambda (conn)
+        (match (lint-warning-message-data->lint-warning-message-ids conn data)
+          (((? string? id1) (? string? id2))
+           #t)))
+      #:always-rollback? #t))
+
+   (test-assert "double insert"
+     (with-postgresql-transaction
+      conn
+      (lambda (conn)
+        (match (lint-warning-message-data->lint-warning-message-ids conn data)
+          (((? string? id1) (? string? id2))
+           (match (lint-warning-message-data->lint-warning-message-ids conn data)
+             (((? string? second-id1) (? string? second-id2))
+              (and (string=? id1 second-id1)
+                   (string=? id2 second-id2)))))))
+      #:always-rollback? #t))
+
+   (test-assert "single set insert"
+     (with-postgresql-transaction
+      conn
+      (lambda (conn)
+        (match (lint-warning-message-data->lint-warning-message-set-id conn data)
+          ((? string? id1)
+           #t)))
+      #:always-rollback? #t))
+
+   (test-assert "double set insert"
+     (with-postgresql-transaction
+      conn
+      (lambda (conn)
+        (match (lint-warning-message-data->lint-warning-message-set-id conn data)
+          ((? string? id)
+           (match (lint-warning-message-data->lint-warning-message-set-id conn data)
+             ((? string? second-id)
+              (string=? id second-id))))))
+      #:always-rollback? #t))))
+
+(test-end)