Capitalisation in Collection IDs is prohibited.

[rhysrevans3]

Issue
Currently you can not have any capitalisation in the collection id which is not specified in the STAC Collection Spec. This is caused by Elasticsearch not allowing Capitalisation in its index names https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-create-index.html#indices-create-api-path-params

Possible solutions:

1. Allow Collection IDs to be capitalised with the record but force them to lower case when creating/interacting with the item indices. This could cause clashes for Collections with different capitalisation. Collection1 and collection1 would have the same item index.
2. Hex encode Collection IDs. This prevents clashes Collection1 >> 436f6c6c656374696f6e31 and collection1 >> 636f6c6c656374696f6e31. But would make discerning between collection within Elasticsearch more difficult.
3. Force lower case and hex encode. collection1_436f6c6c656374696f6e31 collection1_636f6c6c656374696f6e31. This would limit the issue of discerning collections to those with identical case insensitive names.

Note: aliases allow capitalisation so could be used in combination with any of the above solutions.