Add clarification for media type

All media types declared with IANA registered the same subtype. This
commit addresses it.

In addition, this commit makes the Content-Type for request and
responses normative with `MUST be`.

Closes ietf-wg-privacypass#33

Author: thibmeu

Diff for: draft-ietf-privacypass-batched-tokens.md

@@ -222,7 +222,7 @@ The structure fields are defined as follows:
 
 The Client then generates an HTTP POST request to send to the Issuer Request
 URL, with the BatchTokenRequest as the content. The media type for this request
-is "application/private-token-privately-verifiable-batch-request". An example
+MUST be "application/private-token-privately-verifiable-batch-request". An example
 request for the Issuer Request URL "https://issuer.example.net/request" is shown
 below.
 
@@ -324,7 +324,7 @@ The structure fields are defined as follows:
   Scalar values, computed as `concat(SerializeScalar(proof[0]),
   SerializeScalar(proof[1]))`, where Ns is as defined in {{OPRF, Section 4}}.
 
-The Issuer generates an HTTP response with status code 200 whose content
+The Issuer MUST generate an HTTP response with status code 200 whose content
 consists of TokenResponse, with the content type set as
 "application/private-token-privately-verifiable-batch-response".
 
@@ -456,7 +456,7 @@ The structure fields are defined as follows:
 
 The Client then generates an HTTP POST request to send to the Issuer Request
 URL, with the BatchTokenRequest as the content. The media type for this request
-is "application/private-token-arbitrary-batch-request". An example request for
+MUST be "application/private-token-arbitrary-batch-request". An example request for
 the Issuer Request URL "https://issuer.example.net/request" is shown below.
 
 ~~~
@@ -509,7 +509,7 @@ prefixed with two bytes. OptionalTokenResponse.token_response is a
 length-prefix-encoded TokenResponse, where a length of 0 indicates that the
 Issuer failed or refused to issue the associated TokenRequest.
 
-The Issuer generates an HTTP response with status code 200 whose content
+The Issuer MUST generate an HTTP response with status code 200 whose content
 consists of TokenResponse, with the content type set as
 "application/private-token-arbitrary-batch-response".
 
@@ -592,7 +592,7 @@ Type name:
 
 Subtype name:
 
-: private-token-request
+: private-token-privately-verifiable-batch-request
 
 Required parameters:
 
@@ -620,7 +620,8 @@ Published specification:
 
 Applications that use this media type:
 
-: Applications that want to issue or facilitate issuance of Privacy Pass tokens,
+: Applications that want to issue or facilitate issuance of Privacy Pass
+  Batched Privately Verifiable tokens as defined in {{batched-private}},
   including Privacy Pass issuer applications themselves.
 
 Fragment identifier considerations:
@@ -665,7 +666,7 @@ Type name:
 
 Subtype name:
 
-: private-token-response
+: private-token-privately-verifiable-batch-response
 
 Required parameters:
 
@@ -693,7 +694,8 @@ Published specification:
 
 Applications that use this media type:
 
-: Applications that want to issue or facilitate issuance of Privacy Pass tokens,
+: Applications that want to issue or facilitate issuance of Privacy Pass
+  Batched Privately Verifiable tokens as defined in {{batched-private}},
   including Privacy Pass issuer applications themselves.
 
 Fragment identifier considerations:
@@ -738,7 +740,7 @@ Type name:
 
 Subtype name:
 
-: private-token-request
+: private-token-arbitrary-batch-request
 
 Required parameters:
 
@@ -766,7 +768,8 @@ Published specification:
 
 Applications that use this media type:
 
-: Applications that want to issue or facilitate issuance of Privacy Pass tokens,
+: Applications that want to issue or facilitate issuance of Privacy Pass
+  Arbitrary Batched tokens as defined in {{batched-arbitrary}},
   including Privacy Pass issuer applications themselves.
 
 Fragment identifier considerations:
@@ -811,7 +814,7 @@ Type name:
 
 Subtype name:
 
-: private-token-response
+: private-token-arbitrary-batch-response
 
 Required parameters:
 
@@ -839,7 +842,8 @@ Published specification:
 
 Applications that use this media type:
 
-: Applications that want to issue or facilitate issuance of Privacy Pass tokens,
+: Applications that want to issue or facilitate issuance of Privacy Pass
+  Arbitrary Batched tokens as defined in {{batched-arbitrary}},
   including Privacy Pass issuer applications themselves.
 
 Fragment identifier considerations: