ability to edit campaign targeting (related to market)

[Ivshti]

it would help a lot to find the right target for your campaign/adunit

needs to be implemented in:

• the platform (this repo)
• the market (to serve the edited targeting info along with /campaigns)
• the adview (to respect it)

needs https://github.com/AdExNetwork/adex-adview-manager/issues/14

[Ivshti]

this was implemented a long time ago