Issue #3055193 by catch, martin107, jungle, mikelutz, longwave, andypost, alexpott, mondrake, tim.plunkett, larowlan: [Symfony 5] The "Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesser" class is deprecated since Symfony 4.3, use "Symfony\Component\Mime\MimeTypes" instead

Issue #3072076 by JordanDukart, logickal, gabesullice, cgoffin, patrickfweston, Wim Leers, alexpott, scuba_fly, larowlan, nehiryeli, xjm, borisson_: JSON:API returns a CacheableResponseInterface instance for non-cacheable methods; causes unnecessary exceptions

Issue #3122113 by Suresh Prabhu Parkala, rpayanm, ilgnerfagundes, gabesullice, bbrala, alexpott, xjm: Convert all PHPDoc links targeting JSON:API contrib issues to target Drupal core issues

Issue #3142934 by jungle, mondrake, longwave, Krzysztof Domański, DevJoJodae, Chi, xjm, catch, andypost: Replace \Drupal\Component\Utility\Bytes::toInt() with \Drupal\Component\Utility\Bytes::toNumber() due to return type

(cherry picked from commit 54cc80e4db3bb543156287e0321e76c64db2a87e)

Issue #3115772 by saurabh.rocksoul, swatichouhan012, Wim Leers, alexpott: User::load calls should be avoided in classes, use dependency injection instead in jsonapi module

Issue #3121362 by jungle, Meenakshi.g, dww, xjm, alexpott, tim.plunkett: Fix duplicate word typos (the the, to to, etc.) for code comments

Issue #3103993 by Hardik_Patel_12, Rangaswini, alexpott: Value returned from FileSystem methods are not checked in streamUploadData() function

Issue #3080259 by gabesullice, alexpott, Wim Leers: Links with different target attributes are improperly merged

Issue #3023015 by Berdir, kim.pepper, tinko, mikelutz: Replace usages of deprecated constants in file.inc

Issue #3014277 by gabesullice, e0ipso, Wim Leers, larowlan, jibran, ndobromirov, catch: ResourceTypes should know about their fields

Issue #3036285 by gabesullice, Wim Leers, Spokje, larowlan, catch: Add a \JsonApiResource\Relationship object to carry relationship data, metadata and a link collection

Issue #3070204 by gabesullice, ravi.shankar, Wim Leers, mglaman, catch, larowlan, jibran: Refactor the JSON:API FieldResolver to use a resource type instead of an entity type ID and bundle ID pair

Issue #3057175 by Wim Leers, gabesullice, Berdir: Implementation of user name in JSON:API can result in overwriting data

Issue #3052954 by Wim Leers, gabesullice, garphy: Incorrect use of UnprocessableHttpEntityException in EntityResource::deserialize()

Revert "Issue #3029540 by mikelutz, catch, alexpott, larowlan, Gábor Hojtsy: [Symfony 4] Sub class \Symfony\Component\Validator\ConstraintViolation and use that in \Drupal\Core\TypedData\Validation\ExecutionContext::addViolation()"

This reverts commit 20496dd2.

Issue #3029540 by mikelutz, catch, alexpott, larowlan, Gábor Hojtsy: [Symfony 4] Sub class \Symfony\Component\Validator\ConstraintViolation and use that in \Drupal\Core\TypedData\Validation\ExecutionContext::addViolation()

Issue #2843147 by Wim Leers, e0ipso, gabesullice, dagmar, xjm, effulgentsia, webchick, dww, Berdir, dawehner, colan, mgalalm, govind.maloo, das-peter, jludwig, ndobromirov, martin107, abhisekmazumdar, nuez, catch, amateescu, pwolanin, mallezie, borisson_, jibran, voleger, plach, GeduR, Grimreaper, apupiales, Sutharsan, RenatoG, michaellander, sergesemashko, dbt102, hampercm, dremy, rpayanm, chriscalip, tstoeckler, keopx, skyredwang, Spleshka, RajeevK, matthew.perry, kaysenlau, jazzdrive3, dsdeiz, ebeyrent, acbramley, deviantintegral, samuel.mortenson, DamienMcKenna, mohit_aghera, ibustos, dpolant, garphy: Add JSON:API to core as a stable module