Feat/if none match

[nick-rv]

Precondition headers management factorized (including if-none-match for instance).

For information:

• a route /etags/purge has been added to allow to purge the cache content through the REST service. (For test purpose for instance)
• After refactoring, the handleItem() function computes now the GET/PUT/PATCH requests on a feature : /collections/{id}/items/{fid} /collections/{id}/items/{fid}.{fmt}

[benoitdm-oslandia]

Rework, mock tests are OK. Need to review db tests

[github-actions[bot]]

Package	Line Rate	Health
github.com/CrunchyData/pg_featureserv/internal/api	89%	✔
github.com/CrunchyData/pg_featureserv/internal/conf	53%	❌
github.com/CrunchyData/pg_featureserv/internal/cql	66%	➖
github.com/CrunchyData/pg_featureserv/internal/data	61%	➖
github.com/CrunchyData/pg_featureserv/internal/service	68%	➖
github.com/CrunchyData/pg_featureserv/internal/ui	82%	✔
github.com/CrunchyData/pg_featureserv/internal/util	73%	➖
github.com/CrunchyData/pg_featureserv	22%	❌
Summary	68% (6152 / 9001)	➖

Minimum allowed line rate is 60%

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
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8 Code Smells

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0.0% Duplication