Setup a 4096 bytes upper bound limit on certificate

I wasn't not able to find an upper bound limit on a single PEM certificate, but looking at the
openssl source code and `OPENSSL_RSA_MAX_MODULUS_BITS` 2048 bytes, by doubling that number
information we should accomodate any certificate metadata.

README.md

@@ -382,7 +382,7 @@ As an example in the case of Filebeat and the TCP input, the `version` field wou
 | Field  | Description  | Type  | Multi Field  | Example  |
 |---|---|---|---|---|
 | <a name="tls.version"></a>`tls.version`  | TLS version  | keyword  |   | `TLSv1.2`  |
-| <a name="tls.certificates"></a>`tls.certificates`  | An array of certificates.  | text  |   |   |
+| <a name="tls.certificates"></a>`tls.certificates`  | An array of certificates.  | keyword  |   |   |
 | <a name="tls.servername"></a>`tls.servername`  | Server name requested by the client.  | keyword  |   | `localhost`  |
 | <a name="tls.ciphersuite"></a>`tls.ciphersuite`  | Name of the cipher used for the communication.  | keyword  |   | `ECDHE-ECDSA-AES-128-CBC-SHA`  |
 

schema.csv

@@ -120,7 +120,7 @@ source.ip,ip,0,
 source.mac,keyword,1,
 source.port,long,1,
 source.subdomain,keyword,1,
-tls.certificates,text,0,
+tls.certificates,keyword,0,
 tls.ciphersuite,keyword,0,ECDHE-ECDSA-AES-128-CBC-SHA
 tls.servername,keyword,0,localhost
 tls.version,keyword,0,TLSv1.2

schemas/tls.yml

@@ -17,9 +17,10 @@
 
       example: TLSv1.2
     - name: certificates
-      type: text
+      type: keyword
       description: >
         An array of certificates.
+      ignore_above: 4096
     - name: servername
       type: keyword
       description: >

template.json

@@ -624,8 +624,8 @@
         "tls": {
           "properties": {
             "certificates": {
-              "norms": false,
-              "type": "text"
+              "ignore_above": 4096,
+              "type": "keyword"
             },
             "ciphersuite": {
               "ignore_above": 1024,