README update SODA-pure

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 may be launched by the following **compose.yaml**.

Docker image is available in this repository and may be launched by an **compose.yaml** as in this example:

```yaml

version: '3' 

```

The above configuaration assumes:

The port number, ACCESS_CONTEXT_ROOT and directory to FITS-files must be adjusted for the given instance.

The above configuration example 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`

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

* identified by SODA-param ID which is an **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: