Context type merging conflicts are confusing

[jasonkuhrt]

Perceived Problem

• https://github.com/graphql-nexus/nexus/pull/1295#discussion_r461447486
• we use declaration merging to merge different context contributions
• if any fields overlap but have different types there will be a hard TS error
• if developer is the overrider but doesn't know about the pre-existnig type he may be confused about what is going on
• if the developer provided the existing type but a plugin overrides he/she may be confused about what is going on
• if developer did nothing, but two plugins collide, he/she may be even more confused about what is going on

Ideas / Proposed Solution(s)

• clear feedback when collisions happen

  1. Where did the current entry come from?
  2. Where dit the new conflicting entry come from?

• if we want to allow runtime to do context entry overwriting (not deep merging but literally wipe out the previous value) then we need a custom type merge instead of relying on declaration merging