Add page composing and promote micro frontends to adopt

radar/2021-01-01/micro-frontends.md

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+---
+title:      "Micro Frontends"
+ring:       adopt
+quadrant:   methods-and-patterns
+---
+
+The Micro Frontends approach continues to prove to be a valuable pattern for large-scale systems developed by several teams. Therefore, we moved this pattern to "adopt".

radar/2021-01-01/page-composing.md

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+---
+title:      "Page Composing"
+ring:       trial
+quadrant:   methods-and-patterns
+---
+
+Page composing is a way to aggregate multiple independent page fragments into one combined web page. As an implementation of [Micro Frontends](methods-and-patterns/micro-frontends.html), this approach supports to deploy and run services agnostic to the technologies used per team.
+
+The concept builds upon the fact that all involved services deliver valid HTML as their output. Our solution is a small application which takes care of gathering the page fragments from all services and composing each into a defined HTML template. A configuration layer further allows to control which fragment gets pulled from the serving instance.
+
+With such a page composing application in place, teams can autonomously develop, deploy and operate their service with the freedom of choosing technologies and release strategies.
+
+Martin Fowler et al. described this as [Server-side template composition](https://martinfowler.com/articles/micro-frontends.html#Server-sideTemplateComposition).