Bump to v0.4.0

[CasperWA]

With the new changes to the schema/models, we need to up the minor version.

Changes:

• Reorder test files and update testing endpoints setup (Reorder tests #162, @CasperWA)
• Separate the regular and index-meta database server, making sure they're not importing each other (Redirect slashed URLs #160, @CasperWA)
• Introduce Starlette/FastAPI HTTP middleware for redirecting URLs ending with a slash to URLs not ending with a slash (Redirect slashed URLs #160, @CasperWA)
• Fix validation of dimension_types resulting in response_fields failing and add tests for response_fields (New REQUIRED level properties #153, @CasperWA)
• Update entry list property descriptions according to updated OPTiMaDe spec (New REQUIRED level properties #153, @CasperWA)
• Validate updated entry list properties and test updated entry list properties (New REQUIRED level properties #153, @ml-evs)
• Add OpenAPI schema descriptions for query parameters (Describe query parameters in OpenAPI schema #166, @CasperWA)
• Remove custom constrained types NonnegativeInt and conlist and use instead standard types together with pydantic's FieldInfo parameters for schema generation and validation (Describe query parameters in OpenAPI schema #166, @shyamd, @CasperWA)

[codecov]

Codecov Report

Merging #168 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #168   +/-   ##
=======================================
  Coverage   86.17%   86.17%           
=======================================
  Files          39       39           
  Lines        1823     1823           
=======================================
  Hits         1571     1571           
  Misses        252      252

Flag	Coverage Δ
#unittests	86.17% <ø> (ø)	⬆️

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