docs: simplify middleware based sequence

[mrmodise]

Suggestion

At the moment, the REST middleware sequence page is mixing explanations with how-to guides and advanced topics. This makes it difficult for our users to find the relevant content (a recipe to achieve the outcome they want).

I propose simplifying this section by applying recommendations from the Acceptance criteria below:

Acceptance criteria

• Further introduce all types of middleware based sequences without going into too much details after use the sequence in your REST application. Additionally, have a Common Task section (see Common Task for reference) with links to the variations of the middleware based sequences for the user to decide, which flavour they want to read further on

• Following up to point 1 move sections Default Sequence, Middleware as actions and Extend the middleware sequence and Custom sequences to own pages

• Move Migrate from legacy sequence to "How-to guides" adding more details that compare the legacy and middleware based sequence. For example, how was error handling done in Legacy and how is it done in the new

• Move Advanced topics to own page and reference it in Common Task section, as per point 1

• Move Query string parameters and path parameters to own page and reference it in Common Task section as per previous point. Not sure how this fits in this section?

• Move Parsing Requests to own page and reference it in Common Task section as per previous point. Not sure how this fits in this section?

• Move Working with Express middleware to own page and reference it in Common Task section as per previous point

[mrmodise]

I will take this