Truncate ID to 64 chars

[cachrisman]

Updated asset_id_from_name to truncate the returned id to 64 characters as Contentful's API doesn't allow more than 64 characters. See https://www.contentful.com/developers/docs/references/content-management-api/#/introduction/resource-ids

[dlitvakb]

Hey @cachrisman,

Thanks for the contribution.

There are 2 things that raise warnings from this and would love to have improved:

1. This will allow for collisions, E.g. a_veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeery_long_asset_name_1 and a_veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeery_long_asset_name_2 would both get truncated to a_veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeery_long_asset_name leading to a collision which we do not want. Better have it then SHA1 hash it + base62 encode it or something alike on longer IDs so that this issue is avoided.

2. Please add a test so that we can check that the asset ID is being generated as expected.

Please let me know if you can do this changes.

Cheers