Adjust CORS policy

[dpwiessner]

The ingestor must be accessible from the PSI URL (*.psi.ch). For development purposes, it would also be good to release localhost or 127.0.01 addresses.

Currently, all requests from a different address are blocked by the CORS policy.

[dpwiessner]

Could be solved using CORS Middleware:

Don't use AllowAllOrigins; put restrictions to the urls we need.

As an idea:

Import: "github.com/gin-contrib/cors"

And add this to NewIngesterServer

    // This is how you set up a basic gin router
    r := gin.Default()

    r.Use(cors.New(cors.Config{
        **AllowAllOrigins: true,**
        AllowMethods:    []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
        AllowHeaders:    []string{"Origin", "Content-Type", "Accept"},
    }))