ZCS-13176 : Add mail recall message verification header

[shubhamCS03]

Requirement of ticket [ZCS-13176]

Requirements:

• To make sure we don't recall a message accidentally or spoofed, we should add a header to outgoing email.
• We need to a header field, Message-Verification , and verify the message-Id while recalling a mail.
• Need to Hash data by using algorithm SHA256 and further encrypt the data by using base64.

Solution:

• A new header field is added while sending mail, Message-Verification which contains hash(algorithm name) and guid(base64 of the guid's hash).
• The Message-Verification header field contains the following required tags, separated by semicolons (with no white space within):
  hash=[string] --the algorithm used to produce the hash value in the "guid" tag. Current valid values are "SHA1" and "SHA256" [[SHA]].
  guid=[base64] --the base64 encoding [[Base64]] of the hash of a globally unique ID (GUID) for the message, using the hash algorithm specified in the "hash" tag. The actual GUID (the pre-image of the hash) is kept secret by the sending side.
• We have created one LDAP attribute secretKeyForMailRecall at global level to store secretKey.
• We have created one SOAP API to generate secretKey.
• We have generate the secretKey using this SHA1PRNG and saved in LDAP attribute secretKeyForMailRecall .
• GUID(globally unique ID) = Message-Id + Date + From + secretKey.

Testing:

• Changes are tested by sending an email and by checking its show original in the header field we are able to see Message-Verification .
• Also tested by decrypting the hash by using base64 we get the same value.

[CLAassistant]

All committers have signed the CLA.

[shrutig0510]

remove extra space

[shubhamCS03]

done