Sample Decryption and Redirects for Epic

[averyniceday]

Fix # (see https://help.github.com/en/articles/closing-issues-using-keywords)

Describe changes proposed in this pull request: Add support for new endpoints that handle redirects from Epic. Includes calls to Mpath server for decrypting IDs before generating redirects. Includes the following additions:

• Endpoint (/api-legacy/epic/sample/{sampleID}): takes an encrypted sample ID, decrypts, and redirects to the appropriate sample
• Endpoint (/api-legacy/epic/patient/{patientID}): takes an encrypted patient ID, decrypts, and redirects to the appropriate patient
• Endpoint (api-legacy/epic/{sampleID}/exists): takes encrypted sampleID, decrypts, and checks for existence (for determining whether to add a linkout from Epic)
• Property (mpath.token): optional, contains api-key for using the decryption server
• Property (mpath.decryption_url): optional, contains URL to decryption server

Checks

• [ ] The commit log is comprehensible. It follows 7 rules of great commit messages. We can fix this during merge by using a squash+merge if necessary
• [ ] Has tests or has a separate issue that describes the types of test that should be created. If no test is included it should explicitly be mentioned in the PR why there is no test.
• [ ] Is this PR adding logic based on one or more clinical attributes? If yes, please make sure validation for this attribute is also present in the data validation / data loading layers (in backend repo) and documented in File-Formats Clinical data section!
• [ ] Make sure your PR has one of the labels defined in https://github.com/cBioPortal/cbioportal/blob/master/.github/release-drafter.yml

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