Fix how email dates are inserted in to PostgreSQL

Previously, the timezone was stripped off, so the timestamps were off. This
commit changes the code to use a Unix timestamp, which avoids this issue.

guix-data-service/branch-updated-emails.scm

@@ -53,7 +53,7 @@
                                      "NULL"
                                      x-git-newrev)
                                  git-repository-id
-                                 (date->string date "~4"))
+                                 date)
 
         (unless (string=? "0000000000000000000000000000000000000000"
                           x-git-newrev)

guix-data-service/model/git-branch.scm

@@ -13,12 +13,12 @@
    conn
    (string-append
     "INSERT INTO git_branches (name, commit, git_repository_id, datetime) "
-    "VALUES ($1, $2, $3, $4) "
+    "VALUES ($1, $2, $3, to_timestamp($4)) "
     "ON CONFLICT DO NOTHING")
    (list name
          commit
          git-repository-id
-         datetime)))
+         (date->string datetime "~s"))))
 
 (define (git-branches-for-commit conn commit)
   (define query

tests/model-git-branch.scm

@@ -1,4 +1,5 @@
 (define-module (test-model-git-branch)
+  #:use-module (srfi srfi-19)
   #:use-module (srfi srfi-64)
   #:use-module (guix-data-service database)
   #:use-module (guix-data-service model git-repository)
@@ -18,7 +19,7 @@
                                    "master"
                                    "test-commit"
                                    id
-                                   (strftime "%c" (gmtime (current-time)))))
+                                   (current-date)))
         #t)
       #:always-rollback? #t))))