Clarify representation of context URLs in JSON payloads

[ralfhandl]

Context URLs may include characters outside of the unreserved set, e.g. a '(', ')', '/' like for a collection of entities reached via a path to a containment navigation property: "$metadata#set('<key_value>')/cont_nav_prop"

Some implementations return such a context URL in a JSON payload with percent-encoded '(', ')', '/', e.g. "$metadata#set%28'<key_value>'%29%2Fcont_nav_prop", others return it with plain characters.

Question is if servers are free to choose the representation of context URLs and service consumers must be prepared to do a percent-decoding before interpreting the context URL

References:

• The JSON Format specification in section 4.3 Relative URLs mention colons inside the path part that must be percent-encoded
• The ABNF includes a statement for the grammar on the necessity of a percent-decoding a URL before parsing it. Shall this rule also be applied for URLs in JSON payloads?

Proposal

Context URLs for contained entities MUST use parenthesis-style keys.

Context URL fragments MUST NOT be percent-encoded, not even key values for contained entities.

Imported from ODATA-1583