Phoenix 1.6/1.7 support

[abpaul]

We are in the process of upgrading our Phoenix project from version 1.5 to 1.6, with plans to further upgrade to 1.7. As part of this transition, we need to update several dependencies, including phoenix_html. However, we're currently blocked because Coherence's dependencies haven't been updated to support the newer versions of phoenix_html.

Are there any plans in updating the dependencies and if not, can we open a PR that sorts that out? Asking as there are a couple of PRs open which haven't been merged or looked at.