Database schema optimization - part 10

tests/resources/jmap/email_snippet/html.eml

@@ -7,6 +7,7 @@ To: Heinz =?iso-8859-1?Q?M=FCller?= <mueller@example.com>
 From: Doug Sauder <dwsauder@example.com>
 Subject: =?iso-8859-1?Q?Die_Hasen_und_die_Fr=F6sche?=
 Mime-Version: 1.0
+Content-Language: de
 Content-Type: text/html; charset="iso-8859-1"
 Content-Transfer-Encoding: quoted-printable
 

tests/resources/jmap/email_snippet/subpart.eml

@@ -2,6 +2,7 @@ From:  Al Gore <vice-president@whitehouse.gov>
 To:  White House Transportation Coordinator
      <transport@whitehouse.gov>
 Subject: [Fwd: Map of Argentina with Description]
+Content-Language: en
 Content-Type: multipart/mixed;
               boundary="D7F------------D7FD5A0B8AB9C65CCDBFA872"
 

tests/resources/jmap/email_snippet/text_plain.eml

@@ -1,5 +1,6 @@
 From: Abidjan Prince <your_prince@gmail.com>
 To: Bill Foobar <foobar@example.com>
+Content-Language: en
 Subject: Help a friend from Abidjan Côte d'Ivoire
 
 When my mother died when she was given birth to me, my father took me so  

tests/resources/jmap/email_snippet/text_plain_chinese.eml

@@ -1,5 +1,6 @@
 From: "孫子" <sun.tzu@wu.state>
 To: "Bill Foobar" <foobar@example.com>
+Content-Language: zh
 Subject: 孫子兵法
 
 <"孫子兵法：">