Atom syndication format

[mgazanayi]

Please take a look at the ATOM RFC https://tools.ietf.org/html/rfc4287

[fbiville]

There are still a few things we need to support:

• section 3.1.1 : "type" attribute should be only "text", "html" or "xhtml". Text constructs MAY have a type attribute (it seems section 4.1.2 also allows arbitrary MIME types because contents can be encoded in Base64 but, as section 4.1.3.1 says MUST NOT be a composite type (see Section 4.2.6 of [MIMEREG]))
• section 3.2 : Author is a Person, Person should have a URI
• section 3.3 : Atom-JAXB should be in charge of properly converting dates?
• section 4.1.1 :
  • feeds still lack "category" attribute (atom:feed elements MAY contain any number of atom:category elements.
  • author should be a collection (atom:feed elements MUST contain one or more atom:author elements)
  • entry equals/hashcode is broken, it should be based on id AND updated (If multiple atom:entry elements with the same atom:id value appear in an Atom Feed Document, they represent the same entry. Their atom:updated timestamps SHOULD be different.)
• section 4.1.2 :
  • entry author should be a collection (atom:entry elements MUST contain one or more atom:author elements, unless the atom:entry contains an atom:source element that contains an atom:author element or, in an Atom Feed Document, the atom:feed element contains an atom:author element itself., i.e. there may be several author)
  • validation is missing on the summary:

atom:entry elements MUST contain an atom:summary element in either of the following cases:
      *  the atom:entry contains an atom:content that has a "src"
         attribute (and is thus empty).
      *  the atom:entry contains content that is encoded in Base64;
         i.e., the "type" attribute of atom:content is a MIME media type
         [MIMEREG], but is not an XML media type [RFC3023], does not
         begin with "text/", and does not end with "/xml" or "+xml"

• section 4.1.3.2 : Contents lack a 'src' attribute (IRI). Validation is also needed, if src is present, then type cannot be "html"/"xhtml"/"text".
• section 4.2.5 : maybe change the type of uri in Icon, String is way too lenient.
• section 4.2.6 : idem for id for Feed & Entry (validation of id should follow what's explained in the spec)
• section 4.2.7 : Link should also have hreflang (Locale?) & length (long)

[coveralls]

Changes Unknown when pulling e404573 on atom_syndication_format into * on master*.