Unclear AccessMethod interpretations

[trbica]

While working on integrating several implementations of DRS we stumbled upon different interpretations of AccessMethod values, specifically type and region values. In the current DRS specification 1.2.0 we have the next definitions:

• type - Type of the access method. Enum: "s3" "gs" "ftp" "gsiftp" "globus" "htsget" "https" "file"
• region - Name of the region in the cloud service provider that the object belongs to.
• access_id - An arbitrary string to be passed to the /access method to get an AccessURL. This string must be unique within the scope of a single object. Note that at least one of access_url and access_id must be provided.

We are in a spot that some DRS implementations in the Get info about a DrsObject response provide s3 type of access which directly provide s3 access_url BUT also provide access_id in the same response and that will give https access_url value (usually Signed URL from that cloud provider) which is something that is hard to work with. This should be addressed through this issue ticket.
Also, region is only bound to cloud service providers and not something that can be bound to file or ftp type, as an example. Some implementations put type to be 'https' and then in the region put, for example, s3.us-east-1.

There should be a strict distinction between accessing cloud resources and other types of access methods in the specification and that should not be interpreted by implementers.

[ianfore]

Much in common with #341 and #360