Bump apollo-client from 2.5.1 to 2.6.1 in /backend

[dependabot-preview]

Bumps apollo-client from 2.5.1 to 2.6.1.

Changelog

Sourced from apollo-client's changelog.

Apollo Client (2.6.1)

• In all Apollo Client packages, the compilation of lib/bundle.esm.js to lib/bundle.cjs.js and lib/bundle.umd.js now uses Babel instead of Rollup, since Babel correctly compiles some edge cases that neither Rollup nor TypeScript compile correctly.
  
  @​benjamn in #4911

Apollo Cache In-Memory 1.6.1

• Pretend that __typename exists on the root Query when matching fragments.
  
  @​benjamn in #4853

Apollo Utilities 1.3.1

• The isEqual function has been reimplemented using the lodash.isequal npm package, to better support circular references. Since the lodash.isequal package is already used by react-apollo, this change is likely to decrease total bundle size.
  
  @​capaj in #4915

Apollo Client (2.6.0)

• In production, invariant(condition, message) failures will now include
  a unique error code that can be used to trace the error back to the
  point of failure.
  
  @​benjamn in #4521

Apollo Client 2.6.0

• If you can be sure your application code does not modify cache result objects (see freezeResults note below), you can unlock substantial performance improvements by communicating this assumption via

  new ApolloClient({ assumeImmutableResults: true })

  which allows the client to avoid taking defensive snapshots of past results using cloneDeep, as explained by @​benjamn in #4543.

• Identical overlapping queries are now deduplicated internally by apollo-client, rather than using the apollo-link-dedup package.
  
  @​benjamn in commit 7cd8479f

• The FetchPolicy type has been split into two types, so that passing cache-and-network to ApolloClient#query is now forbidden at the type level, whereas previously it was forbidden by a runtime invariant assertion:

  export type FetchPolicy =
    | 'cache-first'
    | 'network-only'
    | 'cache-only'
    | 'no-cache'
    | 'standby';
  
  export type WatchQueryFetchPolicy =
    | FetchPolicy
    | 'cache-and-network';

  The exception thrown if you ignore the type error has also been improved to explain the motivation behind this restriction.
  
  [Issue #3130 (comment)](https://github-redirect.dependabot.com/apollographql/apollo-client/issues/3130#issuecomment-478409066) and commit cf069bc7

• Avoid updating (and later invalidating) cache watches when fetchPolicy is 'no-cache'.
  

... (truncated)

Commits

• 4db0a73 chore: Publish
• fe4c2ff Update root package-lock.json after adding lodash.isequal.
• 21cfe5d Update CHANGELOG.md with new patch versions.
• 2593f8f Reimplement custom isEqual apollo-utilities function using lodash.isequal (#4...
• 5048b1b Compile ESM bundle to CJS using Babel instead of Rollup. (#4911)
• 4bd8237 docs: fix typo in react-apollo-migration.md (#4893)
• b927458 Merge pull request #4907 from apollographql/renovate/typescript-3.x
• b5af622 Fix TypeScript errors in tests/writeToStore.ts.
• bd0bd82 chore(deps): update dependency typescript to v3.5.1
• f7ecafa chore(deps): update dependency tslint to v5.17.0
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot ignore this [patch|minor|major] version will close this PR and stop Dependabot creating any more for this minor/major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot use these labels will set the current labels as the default for future PRs for this repo and language
• @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language
• @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language
• @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot dashboard:

• Update frequency (including time of day and day of week)
• Automerge options (never/patch/minor, and dev/runtime dependencies)
• Pull request limits (per update run and/or open at any time)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)

Finally, you can contact us by mentioning @dependabot.

[codecov]

Codecov Report

Merging #745 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #745   +/-   ##
=======================================
  Coverage   23.76%   23.76%           
=======================================
  Files         165      165           
  Lines        2323     2323           
  Branches      120      120           
=======================================
  Hits          552      552           
  Misses       1736     1736           
  Partials       35       35