README update (SODA pure config and run)

is a web-application to access astronomical data stored in FITS-files.

It implements SODA IVOA recommendation v1.0 (https://ivoa.net/documents/SODA/20170517/index.html).

Docker image is available in this repository and cean be launched by the following compose.yaml

Docker image is available in this repository and may be launched by the following **compose.yaml**.

```yaml

version: '3' 

      - /srv/ska/surveys:/srv/surveys:z,ro

    restart: always

```

  soda-ssl:

    container_name: soda-ssl-vlkb

    image: git.ia2.inaf.it:5050/vialactea/vlkb-soda/soda:1.6.3

    ports:

      - 18025:8443

    environment:

      - SECURITY=ia2token

      - ACCESS_CONTEXT_ROOT=ska#datasets

    volumes:

      - /srv/ska/surveys:/srv/surveys:z,ro

    restart: always

The above configuaration assumes:

* 'SKA' project holds FITS-files in sub-directories under: `/srv/ska/surveys`

* will be accessed remotely by URL: http://<server>/ska/datasets/soda

* identified by SODA-param ID which is **IVOID** of the form:

`ID=ivo://<authority>/resource-key?<relative-pathname>#extnum`

Note that the service apends **soda** to ACCESS_CONTEXT_ROOT.

The pathname in the ID is relative to the path in compose.yaml volume-mapping (e.g. '/srv/ska/surveys').

The FITS extension number `#extnum` is optional. Default is the primary HDU.

Data access example:

```bash

curl -s -k --get

    --data-urlencode "ID=ivo://some-auth/some-key?some/path/somefile.fits"

    --data-urlencode "CIRCLE=202.256 47.493 0.2"

    -v -o soda.fits

    http://localhost:18019/ska/datasets/soda

```

The URL root `http://localhost:18019/ska/datasets/soda` returns the service descriptor.

## SODA for VLKB