[api, frontend] Endpoints modelization (#268)

.github/PULL_REQUEST_TEMPLATE.md

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+### Proposed changes
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+*
+*
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+### Related issues
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+### Checklist
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+- [ ] I consider the submitted work as finished
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+### Further comments
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+If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...