Truncate access review roles with badge list

Long role strings in the access review table broke row layout when
drivers joined many roles into one comma-separated value. Expose
roles as a string array in GraphQL by splitting the stored role at
the API layer, and render the first three roles as badges with a
"+X more" popover for the rest.

Closes ENG-459.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

pkg/accessreview/drivers/github_test.go

@@ -43,5 +43,5 @@ func TestGitHubDriver(t *testing.T) {
 	r := records[0]
 	assert.NotEmpty(t, r.FullName)
 	assert.NotEmpty(t, r.ExternalID)
-	assert.NotEmpty(t, r.Role)
+	assert.NotEmpty(t, r.Roles)
 }