Serialize smalldata to a blob-less entry in CGDFG

[dehann]

Quirky decision, how about dropping the separate smalldata container, and only maintaining the Data plumbing but allow entries that do not have an associated Blob? We can flag the Entry object as either having a Blob or not (as immutable field in an entry)?

We can use the Entry.description::String field to store a JSONed string that represents the Smalldata interface, and limit its size...

Smalldata functions are then fuss-free wrappers around entries without worrying about what data types, MIME, Entry or Blob.

(bit like Macklemore, bought a broken keyboard): I have a short string, please store the short string...

cc @GearsAD @Affie

Related #403

[GearsAD]

Not a bad idea, I'm about to separate out the big data as separate nodes though, so that may make this difficult.

[GearsAD]

I guess we could still do it, we would just have to collect the entries around the node, but it would be a bit more difficult than a JSON blob inside the actual node.

[Affie]

It fits in with why I originally created the AbstractBigDataEntry (renamed AbstractDataEntry) in our application.
I just stored the data in a custom structure directly. For example, tags were something like:

struct TagData <: AbstractDataEntry
    key::Symbol
    family::String
    tagids::Vector{Int}
    bTt
end

The problem was a concern that the payload could get too big. That's why the in-memory data store was created. I don't like and never used smalldata because of the String, but it can perhaps be consolidated as:

struct SmallData <: AbstractDataEntry
    key::Symbol
    data::String
   #OR 
    smallDataDict::Dict{String, String}
end

I guess smallDataDict::Dict{String, String} would work better as it would just be a JSON blob inside the satellite node if you implement it that way.

[dehann]

Affects JuliaRobotics/Caesar.jl#514

[dehann]

we could if we really wanted to store something like this using a combo of the BlobEntry.description, BlobEntry.metadata, and BlobEntry.mimeType fields.

[dehann]

Also,

julia> UUID("00000000-0000-0000-0000-000000000000")
UUID("00000000-0000-0000-0000-000000000000")