Implement media tagging

[RiccardoM]

Feature description

Currently, when creating a media the user can specified it's URI and MimeType. In order to better support media sharing (particularly images) on a wide range of social networks, we should implement media tagging. Thanks to this features, users will be able to tag other users on a particular image to make sure they are someone recognizes when that image is viewed.

Implementation proposal

In order to implement media tagging, the following changes should be made.

Update he PostMedia type

First of all, we need to update the PostMedia type to be:

type PostMedia struct {
	URI      string           `json:"uri"`
	MimeType string           `json:"mime_type"`
        Tags     []sdk.AccAddress `json:"tags"`     // Contains the list of all the tagged users
}

Update the CLI and REST commands

Then we need to update the CLI and REST commands to allow tagging. The most particular one will be the CLI one. I think the --media flag can be changed to something like:

--media "<URI>,<MimeType>,<Tags...>

So an example could be

--media "https://example.com,image/jpeg,desmos1p7c8h59nrc8e5hxvgvu2g7tpp0xwn4mzevzgg7,desmos1p7ad878nealg249qkkdl9ldxrllst23lklngcx

What are your thoughts on this @bragaz @kwunyeung?

[leobragaz]

I could go with this one, what do you think? @RiccardoM