Reduce duplication in Taxon output from REST api, `all-taxons` is repetitve

**Describe the bug**

Xponents REST api result lists an array of taxon metadata in `all-taxons` -- it balloons if a taxon is repeated in the tagger output.


**To Reproduce**
**Expected behavior**

```
`all-taxons` : [ {unique object}, {unique object} ...]
```
Where unique object is the distinct metadata for the taxon.