Proposal: add concestor link relation

[philvarner]

Related Issue(s):

• Create a new link relation like "parent-catalog" or "api-parent" #239

Proposed Changes:

1. Add concestor link relation to furthest back parent

PR Checklist:

• This PR has no breaking changes.
• This PR does not make any changes to the core spec in the stac-spec directory (these are included as a subtree and should be updated directly in radiantearth/stac-spec)
• I have added my changes to the CHANGELOG or a CHANGELOG entry is not required.

[m-mohr]

I'm not sure I understand. First of all, concestor I've never heard before but I'm also a non-native spreaker. Assuming I'm somewhat "average", this might not be as ituitive as the other relation types.

Also, from the description below I'm not sure what the difference between root and concestor is. Initially, I'd think that if I follow all parent links I'd get to the root. So this likely needs more explanation.

Would this be a good extension as it seems relatively niche?

PS: There are a lot of unrelated changes in this PR. Is this intentional? Makes the review pretty time-consuming.

[m-mohr]

After the discussion yesterday, I think we were coming from different directions. Assuming we are looking at CMR which has a catalog structure as "real" root and a couple of APIs underneath it.

1. Point the root to the API landing pages and point concestor to the "real" root
2. Point the root to the "real" root and something like "parent-api" to the API landing pages

I'm honestly not sure what the initial desire in #239 was, maybe the involved users were actually looking at different use cases, too.
Point 2 feels more logical to me though as calling something root which is not the actual root is confusing. Also I feel it is more explicit. I'd struggle to implement 1 in STAC Browser, I think.

Should APIs that are just "normal" (i.e. root = API landing page) also use "parent-api"? Seems rather repetitive.